These hills were made for use in Battletech. They are simply 3/4" white insulation foam cut to shape with a large razor or box cutter, painted black and flocked. These are nice because it is obvious where the elevations are, like a contour map. They are not the most visually appealing.
This hill is made in the same way. The shapes were cut out using a cheap hot wire cutter from Michaels. There are layers of 3/4" foam stacked on top of each other; pinned together using toothpicks and glued together with white glue. The hill was painted black, coated in white glue, and coated in regular old playground sand. Once dry it was drybrushed progressively lighter shades of brown.
Here are more hills done in a similar style. The desert ones are made by glueing two 3/4" pieces of white foam together and cutting the shape out with a razor blade. A hot wire cutter was then used to carve in the rock face. The hill was painted black, and the rock face was drybrushed. grey and white. Regular fine terrarium sand was glued to the tops.
These hills are carved from some scraps of 2" thick blue insulation foam, but in all other ways made the same way as the desert ones above. I much prefer this to the white foam as it doesn't make such a mess when cutting. Instead of sand on the top I used green ground cover, or flock.
Here is yet another hill with a rock face. This one is different and has a sloping back side. Blue or pink insulation foam is good for these kinds of hills because you can rough cut it with a razor or hot wire cutter, then sand it smooth. The photograph is of some testing I did on this piece by painting the hill green first, and some different types of flock. It didn't turn out well. The hill now has my traditional ground cover on it.
The last two examples of hills I have are of more finish, natural flowing hills. Except for this one:
A 3" piece of pink insulation foam, cut to shape with a razor blade and sanded smooth. I painted it black, and flocked it wiht my standard mix. With this piece I also coated the flock with a layer of white glue to make it more durable. This hill is hard as a rock, and very rough to the touch.
Here are some smaller hills from blue foam for my 15mm WWII skirmish.