I have just begun the basic set building for the flying ship film. I bought 4×8′ sheet of 1″ thick styrofoam insulation from the home store for about $20 US. I cut it with a razor knife, bandsaw, handsaw, and a file. I cut the basic hills and rocks and landscape items, glued them on with liquid nails in a caulking gun, and then paper mached over them. The next step is to apply a layer of flat black paint with a brush since spray paint will melt the foam.
The pepsi can is there for scale.
Go ahead, make a mess, have some fun.