For this project, we had an old dresser laying around. I used a large sheet of 3″ thick styrofoam insulation, cut it into desert rock-ish shapes with a utility knife, gorilla glued it all together, and filled any gaps with spray foam insulation.
After this, I coated all surfaces with 3-4 layers of unsanded grout, and painted the exterior. For the doors, I used plexiglass panes I picked up at The Home Depot for around $10 each. Cutting them to size was harder than I thought, and I ended up breaking two panes in the process, so I had to buy more. I used plastic “U” shaped trim as a door track, which works great.

BEFORE

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