The stones were cut with enormous precision, at least relative to what we know about the available cutting tools. You cannot still stick a knife between a lot of these stones. Maybe we will learn more about that.
I'm pretty sure we've conclusively answered these questions. Hand tools, skill, and absolutely unreasonable amounts of time and patience.
Any master stoneworker from any era should be able to carve stone to that level of precision given enough time and reason. The problem, as always, is that there is usually very little reason to put in that amount of time and effort when you can get 90% as good for 50% the effort.
(I know nothing about this subject, feel free to ignore me.)
My dentist is pretty good at doing this too, by putting marking paper between my teeth and having me bite down. I wonder if a similar technique could be used:
Have the blocks close together, constrained to only move on a single axis by rails or whatever. Drape a thin sheet of material over one of the blocks, the non-moving one (perhaps it's an already-placed one?) Maybe it's something that visibly shows when it's crushed, or maybe it's coated with the blood of the powerless. Smash the other block into it. Pull them apart and look where they made contact. If it's mostly everywhere, done. If not, grind down or chip out the parts that touched. Repeat until you run out of innocents.
To do the very last block, you'd have to meld two sides, remove a block, fix up the other side, and then put it back in. Which might make this testable.
But I'm just pulling stuff out of my nether orifice.
How does ASML make the most modern chips? You mean light and mirrors?