So, I should be crediting a website that I picked this up from years and years ago but I can't remember where I got it from. I will tell you this: they took considerably more care in the design of their structures but I like the crappy look of a poorly planned out building. We are talking ruined buildings after all.I start with an old box, box cutter, ruler/pen, masking tape, drywall joint compound, and a brew.
With minimal planning, i chop the board up and tape it all in place.
Throw some joint compound on the walls.
I do a very crapy job spray painting and call it good.
This one has been around for years.