I'm imagining a roughly tetrahedronal structure. Each side is a right triangle with the lower corners cut off, leaning at a 45 degree angle to meet the edges of the other sides. Each side also has a roughly semicircular hole in it, which would line up with the second floor.

Yes, I got this idea from looking at a plastic shipping brace that came in my air conditioner packaging.

Is there a way to slope the bottom of a wall? If so, I can make a four-sectioned wall with slants, export as furniture, and rotate it appropriately.

Otherwise, I have no idea how to do this.