How did you do this...
I honestly don't know, LSD or some stuff.
But no you start with the roof and basically just build a boat. from there you build the outline of the walls and build up. Kind of pretend it's rightside up. Then you place your windows, which in this case has to be at your legs height instead of eyes, since inverted. The door should be closer to the ceiling than the floor. The floor being the roof in this case. This way it looks like the door, if the house was turned right side up, would be ground level as any normal door. Then you cap it off. The terrain was tricky, I just pretended I was building a cave or just an inverted terrain. Unfortunately the bottom of the bricks make it looks less fluent as the topside, but It was acceptable.