I think you hit the highlights for a volcano board. I like how you aligned the layers straight across the tile. My volcano attempt was a quarter circle in the same area and I retained the cake tier effect for four levels. The quarter circle shape reduced the playable area considerably.
For what it's worth I developed a construction technique/option. It used a cardboard frame/side supports, balled up newspaper filler and expanding foam in the cake tier gaps. Carved away excess foam after it fully expanded and dried then painted the entire thing with a brown paint with crushed granite suspended in it.