Hope you don't mind if I chime in.
I think Ori's points about river levels and the surrounding cemeteries are valid.
The ground layout of the cemeteries has zilch in common with the ground layout of the P'mids.
As they say in cockney rhyming slang, "As pi**ed as a handcart" (I'll let you figure out what handcart rhymes with) lol
I'm pretty sure that water had a lot to do with the construction, but keep in mind that the builders were master surveyors as evidenced by the position of the P'mid relative to the geo pole. If they could get that bang on they'd have had little difficulty in achieving a level over a large area. I would have thought that they'd use a similar method of surveying to achieve a level,
Can you use water to achieve a compass bearing alignment?
I've no idea what methods they used, they could have used water for levelling if they could keep the courses watertight. There may be a problem with evaporation, like a very shallow lake over a large stone surface.
Also there's the problem of getting hundreds of tons of water up there. I'll leave that to you.
Anyway keep up the good work buddy, following you all the way.