[impactplayer]

They use 4 large C-clamps, two on each side of the stones, to form a circle - then rolled them into place. These tools have been found, and the “dimples” left by the C-clamps can been seen.
Simple - - if you have enough workers.

[outofsalt]

"They use 4 large C-clamps, two on each side of the stones, to form a circle - then rolled them into place."

If you didn't have cell phones you might spend a summer doing this as a kid. Kid builds a pyramid and a swimming poolwith ancient skills!