I used cork to make these with & tbh I find cork is one of the best modelling materials I've ever used, its cheap, light weight & is robust enough that you don't have to handle it with kid gloves.
So for the walls I cut strips of cork into 3 different sizes 20mm, 2.5mm & 15 mm all by 300mm
These where then cut into 20mmx150mm, 2mmx20 & 15mmx15mm, to make up the corner pieces I cut a couple of the 20mmx150mm into 20mmx75mm.
Now really these are as simple as can be to make as all there is to it is glue 4 of the 2mmx20 pieces to the 20mmx150mm strips, two at one end on each side & two in the middle, the 15mmx15mm pieces are then glue on top of the wall over these points.
Just two things to note the two 2mmx20 pieces at the end are let over hang the end of the 20 strip, while at the other end you need to both sides of the 20mm strip a little sanding, this is done for joining the wall pieces together.
That's really all there is to it, I'm not going to base theses wall as I don't think they need it plus it leaves them more flexible use wise.
I've got to say that even though this was such a simple project it was nice to get some little thing done.
Above a corner & a straight section of wall joined together, so until next time thanks for dropping in I hope it was worth your while.