The basic steps have been: 1) cut out the terrain pieces, 2) paint with a brown acrylic the edges of each foam board tier and the outline of the area on which it is placed, 3) place the foam board tier on the grass mat (I'm using a Woodland Scenics product) and cut out a shape that matches the tier, and 4) glue the grass mat section to the tier.
I have yet to place the many trees that covered the battlefield, but this will be a relatively easy task. The next major challenge will be to represent the streams, roads, and fields. Frankly, I'm not sure how to proceed, and suggestions are welcome. As the streams are small, my thought is to trace the course of the streams on the grass, then scrape away some of the grass and paint the cleared area a pale brown. Next I would glue small stones and bits of brush along the stream. Likewise, the best idea I've had for the roads is to scrape away some of the grass and paint the cleared path some kind of brown. As for the fields, I'm planning on gluing onto the battlefield squares of some brown corduroy material.