Amenemhet I was the founder of the 12th dynasty. He was the vizier of his predecessor Mentuhotep IV who he may have assassinated.

The Amenemhet I pyramid at El-Lisht.
Amenmehet I was a vizier of Mentuhotep IV of the previous dynasty. He was not of royal descent. He is thought to have overthrown Mentuhotep IV and founded the 12th dynasty.
The 12th dynasty lasted almost 200 yrs and was essentially the Middle Kingdom of Egypt.
The pyramids of the 12th dynasty characteristically had a core that was made out of mudbricks and an external veneer that was made from limestone.
A large slave labour force was needed to make the mudbricks.
A workers village was found by Petrie in 1891 at Kahun. He found scarabs from the time of Sensuret II that indicated that it was occupied during the 12th dynasty up until the 13th dynasty. He also found evidence of a sudden exodus from the village in the 13th dynasty. He thought that many of the semitic slaves were Isralites.
Joseph came to Egypt at the age of 30 yrs and was 110 yrs when he died. The Jews lived in Egypt 430 years and then Moses lead them out of Egypt (The Exodus). The Israelites numbered only 70 when they came to Egypt in the ?third dynasty. By the 12th dynasty, they numbered over a million and the pharaoh had long forgotten their connection to Joseph (?Imhotep) who had saved Egypt from famine and may even have built the first pyramid.

Amenemhet I – the first pharaoh of the 12th dynasty. He reigned for 30 yrs (including a 10 yr coregency with his son Sensuret I) and then was assassinated.

The Amenemhet III pyramid at Hawara. The Last of the Great Pyramids. Like other 12th dynasty pyramids, the mud bricks in it’s core were probably made by Hebrew slaves.

Amenemhet III was the 6th pharaoh of the 12th dynasty of Egypt. He built 2 pyramids; the Black Pyramid at Dashur and this one at Hawara.
While the pyramids of the Old Kingdom were made of solid limestone blocks, the 12th dynasty (Middle Kingdom) pyramids had a core that was made of bricks (containing mud and straw) and an outer veneer of limestone.
Over the centuries, the outer veneer has fallen down as a result of erosion and earth quakes or stolen by people to be used elsewhere. What remains is the mud brick core which has been eroded further by the weather.
If you look carefully, the straw within the mud bricks is still quite easy to see.
It would have taken an enormous number of slaves to make this number of mud bricks, let a lone assemble them.
It is likely that the mud bricks in these 12th dynasty pyramids were made by Hebrew slaves prior to the Exodus.

Amenemhet III would have been the Pharaoh that Moses fled from.

When the Exodus took place in 1445 BC, there were not enough slaves left in Egypt to make mud bricks  and so no more pyramids were built.
The dates do not match with the traditional dates calculated from Manetho because many dynasties and regencies ran in parallel and some dynasties have been counted twice. The Egyptian Chronology needs to be revised and then it will match the Biblical Chronology.

An ancient historian by the name of Josephus records that the Israelites were given the task of building pyramids.

The 12th dynasty pyramid of Sensuret II (Sesostris II) at Lahun.

The Works of Josephus

Antiquities of the Jews – Book II

CONTAINING THE INTERVAL OF TWO HUNDRED AND TWENTY YEARS.

FROM THE DEATH OF ISAAC TO THE EXODUS OUT OF EGYPT.

 

CHAPTER 9.

CONCERNING THE AFFLICTIONS THAT BEFELL THE HEBREWS IN EGYPT, DURING FOUR HUNDRED YEARS. (16)

1. NOW it happened that the Egyptians grew delicate and lazy, as to pains-taking, and gave themselves up to other pleasures, and in particular to the love of gain. They also became very ill-affected towards the Hebrews, as touched with envy at their prosperity; for when they saw how the nation of the Israelites flourished, and were become eminent already in plenty of wealth, which they had acquired by their virtue and natural love of labor, they thought their increase was to their own detriment. And having, in length of time, forgotten the benefits they had received from Joseph, particularly the crown being now come into another family, they became very abusive to the Israelites, and contrived many ways of afflicting them; for they enjoined them to cut a great number of channels for the river, and to build walls for their cities and ramparts, that they might restrain the river, and hinder its waters from stagnating, upon its running over its own banks: they set them also to build pyramids, (17) and by all this wore them out; and forced them to learn all sorts of mechanical arts, and to accustom themselves to hard labor. And four hundred years did they spend under these afflictions; for they strove one against the other which should get the mastery, the Egyptians desiring to destroy the Israelites by these labors, and the Israelites desiring to hold out to the end under them.

(16) As to the affliction of Abraham’s posterity for 400 years, see Antiq. B. I. ch. 10. sect. 3; and as to what cities they built in Egypt, under Pharaoh Sesostris. and of Pharaoh Sesostris’s drowning in the Red Sea, see Essay on the Old Testament, Append. p. 132-162.

(17) Of this building of the pyramids of Egypt by the Israelites, see Perizonius Orig. Aegyptiac, ch. 21. It is not impossible they might build one or more of the small ones; but the larger ones seem much later. Only, if they be all built of stone, this does not so well agree with the Israelites’ labors, which are said to have been in brick, and not in stone, as Mr. Sandys observes in his Travels. p. 127, 128.

The Pharaohs (of the 12th dynasty) oppressed the Israelites and forced them to make mud bricks reinforced with straw.

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<< Exodus 5 >> New International Version 1984 Bricks Without Straw 1Afterward Moses and Aaron went to Pharaoh and said, “This is what the Lord, the God of Israel, says: ‘Let my people go, so that they may hold a festival to me in the desert.’” 2Pharaoh said, “Who is the Lord, that I should obey him and let Israel go? I do not know the Lord and I will not let Israel go.” 3Then they said, “The God of the Hebrews has met with us. Now let us take a three-day journey into the desert to offer sacrifices to the Lord our God, or he may strike us with plagues or with the sword.” 4But the king of Egypt said, “Moses and Aaron, why are you taking the people away from their labor? Get back to your work!” 5Then Pharaoh said, “Look, the people of the land are now numerous, and you are stopping them from working.” 6That same day Pharaoh gave this order to the slave drivers and foremen in charge of the people: 7“You are no longer to supply the people with straw for making bricks; let them go and gather their own straw. 8But require them to make the same number of bricks as before; don’t reduce the quota. They are lazy; that is why they are crying out, ‘Let us go and sacrifice to our God.’ 9Make the work harder for the men so that they keep working and pay no attention to lies.” 10Then the slave drivers and the foremen went out and said to the people, “This is what Pharaoh says: ‘I will not give you any more straw. 11Go and get your own straw wherever you can find it, but your work will not be reduced at all.’” 12So the people scattered all over Egypt to gather stubble to use for straw. 13The slave drivers kept pressing them, saying, “Complete the work required of you for each day, just as when you had straw.” 14The Israelite foremen appointed by Pharaoh’s slave drivers were beaten and were asked, “Why didn’t you meet your quota of bricks yesterday or today, as before?” 15Then the Israelite foremen went and appealed to Pharaoh: “Why have you treated your servants this way? 16Your servants are given no straw, yet we are told, ‘Make bricks!’ Your servants are being beaten, but the fault is with your own people.” 17Pharaoh said, “Lazy, that’s what you are—lazy! That is why you keep saying, ‘Let us go and sacrifice to the Lord.’ 18Now get to work. You will not be given any straw, yet you must produce your full quota of bricks.” 19The Israelite foremen realized they were in trouble when they were told, “You are not to reduce the number of bricks required of you for each day.” 20When they left Pharaoh, they found Moses and Aaron waiting to meet them, 21and they said, “May the Lord look upon you and judge you! You have made us a stench to Pharaoh and his officials and have put a sword in their hand to kill us.”

The Israelites were fruitful and multiplied while Joseph (?Imhotep) lived. After Joseph had died, a new king came to power in Egypt who did not know Joseph or his connection with the Israelites. He felt threatened and started to oppress the Israelites.

<< Exodus 1 >> New International Version 1984 The Israelites Oppressed 1These are the names of the sons of Israel who went to Egypt with Jacob, each with his family: 2Reuben, Simeon, Levi and Judah; 3Issachar, Zebulun and Benjamin; 4Dan and Naphtali; Gad and Asher. 5The descendants of Jacob numbered seventya in all; Joseph was already in Egypt. 6Now Joseph and all his brothers and all that generation died, 7but the Israelites were fruitful and multiplied greatly and became exceedingly numerous, so that the land was filled with them. 8Then a new king, who did not know about Joseph, came to power in Egypt. 9“Look,” he said to his people, “the Israelites have become much too numerous for us. 10Come, we must deal shrewdly with them or they will become even more numerous and, if war breaks out, will join our enemies, fight against us and leave the country.” 11So they put slave masters over them to oppress them with forced labor, and they built Pithom and Rameses as store cities for Pharaoh. 12But the more they were oppressed, the more they multiplied and spread; so the Egyptians came to dread the Israelites 13and worked them ruthlessly.14They made their lives bitter with hard labor in brick and mortar and with all kinds of work in the fields; in all their hard labor the Egyptians used them ruthlessly.

The last of the Great Pyramids. The Amenmehat III pyramid at Hawara. The 12th dynasty pyramids had a core of mudbricks and a limestone veneer. The limestone veneer has fallen away / been removed over the centuries exposing the core which is composed of millions of mudbricks.

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Mud bricks in the Ameenhet III pyramid at Hawara. This was the last great pyramid to be built.