One of the biggest things that's absolutely killing the building system in this game is that there are only two blocks in the entire game that play well with uneven ground: The concrete blocks and the stilt blocks from the wood floor section of the game.

However, both of these blocks have a huge problem: They interact with the snap grid as floors, not as foundations.

Of course it seems only logical that the thing that goes at the bottom of your house is a floor, however, when you consider how the rules of block snapping work you quickly realize there is an essential problem with this: All of the premade walls snap as floors, which means the will never snap to the top of a concrete block, nor will a concrete block snap to the bottom of a floating house. You have to either manually align your structure on top of a concrete base, or you have to use walls instead of prefabs to build up from the concrete base, because since the prefabs come with integrated floors they cannot be placed on the same level as concrete blocks.

It would really help to build better looking structures in this game if concrete and stilt blocks were available in a "Foundation" variety, that tried to snap to the bottom of floor tiles. That way you could simply create a building, and then go around it and simply snap foundation blocks underneath every place where it doesn't touch the ground. This would be much easier to pull off than having to create a slab of concrete first, and then either having to try to manually align a house with floors on top of it, or having to build the outer walls for the lower level without any prefabs because they have integrated floors just like the concrete.