These hills were initially intended for a 3D Axis and Allies Miniatures board I was making. The technique could easily be used for any other hex based game, like Battletech.
For hills I used the basic foam technique. Each hill is made from 1" thick blue insulation foam. a 2" hex was printed from my PC and cut out. This template was traced onto the foam in the shape of the hill sections I needed.
The hills were then cut out with a razor blade and then smoothed out with a hot wire cutter. The hills were then further smoothed with sand paper. One hill section forms around a single city hex; the inside of this hill was carved to be a rocky cliff. A crochet needle was used to indent the hills along the hex lines.
Initially roads were carved into the hills to match up with the original roads, but after these changed the channel was filled in with plaster and sand glued into place.
The hills were brush primed black, the roads drybrushed from dark brown to light brown to tan. The cliff was drybrushed from dark grey to light grey to white. Once painted, the hills were flocked with the special mix. Care was taken to leave a black line between the hexes.