My recollection is that Heyerdahl rolled the statues from the quarry on beds of logs, which is also how they were depicted being moved in the movie Rapa Nui. That seems to me to be easier and more efficient than the rocking walk depicted here. You need logs to move them by this rolling method, of course, but not too many--once you roll past a log it is carted around to the front and rolled over again (and again, and again...). Once they were in their final locations, Heyerdahl showed it was possible to lift them into place using the pole and pebble technique noted by Amos.
Having the pyramids built of sand would be a surprise to any of us who have actually climbed them. It sure felt like stone to me!
As for the construction technique, I'm in favor of aliens with really efficient sky hooks. Or they may have gone up with the technique described in the demotivator poster: it is amazing what you can accomplish with a little bit of imagination and an unlimited supply of slave labor.