They were able to make level marks on the rock walls. The walls could then be cut to the same height, making the top surface level. The trenches were then filled with rubble. After the surface was level and a solid foundation was formed, the pyramid needed to be centered with each side facing the four directions on a compass. They used astronomy to help them find the exact points.
Theories suggest that a round wall was built to the level of the horizon.
He marked the wall in both points and then calculated where direct north and south would be by bisecting the angle. The pyramid could then be built perfectly square and facing each compass point. While the site was being prepared, the slaves were busy cutting large limestone and granite blocks. Each block was about seven feet high, eighteen feet long and weighed as much as two tons. They cut the limestone with copper chisels, mallets, wedges and lots of hard work.