Cleaning up the walls of an XPS foam diorama block

[pale lotus]

Hi folks, I was a little adventurous when I cut this XPS foam diorama. Now, several steps later I realize that the raw XPS (or painted black) is going to look awful. I made a case of balsa wood, but it's pretty janky. Any suggestions for getting smooth, square walls? Some options I was thinking:

1. Start again and actually measure a square base.
2. Use the balsa wood, fill in the gaps with putty and glue.

Thanks!

[wispy jewel]

If keeping the wood frame, can easily fill in the gaps with foam bits, tinfoil, anything really. Toss on a layer of joint compound or similar and it'll be ready to paint.

If you just want a perfectly clean and square foam block, then I hope you have a hot wire cutter. A really sharp knife might work, but it would be harder to get the vertical angle exactly 90 degrees, especially on such a tall block.
Alternatively, if going the foam-only route, you could texture the sides and paint it like cliffs or something. Would so be very easy.

[broken harness]

Go with the balsa, fill in gaps. If you want a smooth texture, you can add filler over the balsa and sand smooth. On YouTube, Nightshift has several videos on making bases like that (it's scale modeling, but the basing is the same in this case)