I carved out one of the side walls and it was a complete disaster. The styrofoam I'm using isn't great for this, and I made the mistake of trying to do it in my kitchen. Looked like it snowed in my apartment! This is the biggest mistake I've made so far (will be cleaning up tiny styrofoam pieces for a while). Looks like I'll have to pick up the other insulation.

The final piece does look pretty good, though. If it wasn't for all the little styrofoam pieces coming off all the time and making a huge mess, it might be worth it.