Grass Floor shouldn't require multi-floor building knowledge. If you know how to build a wall, a windowed wall and a door I think you also should be able to build a floor.

Agreed. This is also a huge issue as building a base without some sort of foundation is a pain, and people are going to start building their bases before getting to the point of finding clay, or getting multi-floor building. Which means that you'd have to rebuild your base afterwards if you wanted to actually attach walls to floor.

Agreed. It is possible to build scaffold, but not the floor 😕