Don’t do it. Don’t build a 3D dungeon.
I made this in 2003. Other crafters have since learned what I did:
The 1 inch = 5 feet rule doesn’t work. Capes, tails, and weapons hit the walls. You need to make it 1.25″ or 1.5″.
Walls don’t work. Players can’t see over them, and miniatures collide with them. Even low-height walls can get in the way.
If you’re going to do it, make it modular, tile-by-tile.
Give the tiles a base. Don’t set them directly on the play surface, they should be thick.
But I never played with this or the 3D dungeon I bought from a friend. Battlemats are superior.