Hills made from foam seem common. I think cork is a good material. When the edges are torn, it has a nice rocky texture. It's more robust than foam. Creating a landscape with visible rock strata is a good way to walk the line between looking natural and having some flat surface to put a model on.
- That's 9mm plywood. 6mm or maybe thinner would do, but I had an offcut. I bevelled the edge by variously hacking at it with a file, a surform (wood grater thingy) and a dremel.
- Toilet rolls cut to random lengths.
- 6mm cork sheet ripped up. I bought mine from amazon.co.uk. You can get it in craft shops. hacking up an old cork noticeboard would probably be a good way to go.
- (hot) glue gun and lots of it. I filled the inside of the toilet rolls around the edges to stick it good and proper.
I used caulk: mastic gun tube, used to squirt around top of skirting board, and paint over. I built this up in layers. and poked extra bits of cork in occasionally. I put the whole thing in a fan oven at 50 degrees to speed things up. This is still several evening's work. Not that long each evening, but it took a few days.
I flocked it with cork dust.
- coat with PVA
- chuck on cork
- shake off excess
- wait for it to dry
- coat with dilute PVA to bind up any loose bits.
This was repeated 3 or 4 times (with oven acceleration).
I added more random battlefield debris (ork, marine, eldar, ...). Painted and added some sickly looking grass.