Started to experiment with some terrain modelling.
Base is 4mm MDF, the walls are pieces from a plasterboard. Not sure the plaster will be durable enough, but it was really quick to build something useful.
Painted with cheap acrylic paints. Brown for the ground (will add flock on the ground), and three layers of different shades of gray on the stone pieces. The two lighter grays were sort of "wet" dry brushed, turned out ok and it was really fast.