An experiment gone awry
I tried this a few months back - before I was aware of UHU glue. I glued foamcard to CD cases with PVA glue, and carved it to form a mound. Then I pinned the walls in place with, er, pins, to secure them as the PVA set. Wanting the buildings to look like Tudor-style homes, I used slices of balsa to duplicate their appearance.
As it turns out, the bases didn't care for the PVA and so curved up. I am quite happy with the majority of the work, but not so much the bendiness. I found it a bit dispiriting, but am almost ready to give it another go with UHU.