Why do you think that’s difficult to do? You carve a rock into a shape, then you see what gaps there are between that shape and the other shapes and you carve another rock to fit it. And when you have hundreds of people in the quarry carving rocks and years to do it, it gets done.
Well sure - but in these pictures, look at the lower right one, say, there’s no rocks in-between, it’s just one bigass rock perfectly carved to fit another bigass rock, and so on. So at least it had to either be done before placement or using some sort of flexible template such that mortar wasn’t used. Which is pretty neat at least. And given the size, one expects it was an enormous PITA.
Of course it was done before placement. It couldn’t be done after placement. It’s really not hard to carve one shape of a rock to fit another shape of a rock given enough time and patience.
What is so funny to me is that these peoples achieved things like massive irrigation systems that enabled them to feed large populations and complicated textile processing and weaving, but these armchair archaeologists think that the wall is the important thing just because it’s the most prominent feature remaining.
