A thin sheet of foam (1/4" Urethane, 3/16" Foam Board or 1" Expanded Styrene) adhered to your plywood base makes an excellent working surface for many types of models. Paint the foam with latex or acrylic paint of the proper color. This will provide the perfect surface upon which to apply ground cover and makes tree "planting" an easy task.
One of the simpler methods when precise contours are unnecessary is the layered method. The following example of this method requires three 1" sheets of foam the full size of the base. However, in actual practice, you will probably use varying thicknesses.
1. Establish grade points at 1" intervals from your contour map (See figures below).
2. Cut the 0 and 3 contours from your first sheet. Cut contours 1 and 4 from the second, and contours 2, 5 and 6 from the third sheet. Scraps will be used for propping and miscellaneous fill-in. Use a serrated knife or hack saw with a sawing motion when cutting the contours.
3. Glue the levels of foam together with the appropriate glue (see our cement guide) and hold in position with nails until the glue dries (allow at least 24 hours). Consider nail placement so they will not affect contour shaping later.
4. With a hobby knife, cut the first contour elevation from your contour map and tack to the appropriate level of foam. With this as your guide, using a serrated knife or hobby knife, roughly trim off the excess foam from that level. Repeat this process until all levels have been trimmed. Remove contour map pieces.
5. Using coarse sandpaper and caution as foams sand easily, sand the contours smooth.
6. Paint the foam a color that will be a suitable undercoat for your finished landscape. Use latex or acrylic paint. OR, see our Polyterrain or Magic Earth materials.