4' x 4' board for Warmachine or three pieces for a 4' x 6' board for Warhammer. It's not the most ideal playing surface, but it works and it only cost me about $20.
For terrain I picked up a 2' x 8' pieces of blue insulating foam. You can get this at Lowes or Home Depot for pretty cheap. I used my Woodland Scenics hot wire to cut irregular shapes into the foam to create terrain. I also used spray adhesive to glue multiple layers of foam on top of each other to get more height out of my piece of terrain. These are the first two pieces I came up with.
On this first piece I shaped three pieces of the 1" thick foam with the hot wire, glued them together with spray adhesive, and put a little woodland scenics foam putty on it to fill some seams and give it a little more texture. I also sanded the top edge and a few other places with some 220 grit sand paper to taper some edges down a bit.
On this next piece I shaped three small pieces of foam this time though splitting them in half to get the wall thickness to about a half inch. I also cut a piece of foam core for the base and tapered the edges down with sand paper. I made the grooves in the wall with a ball point pen and just pressed into the foam. Lastly I glued the pieces onto the base.
Here are the two finished products. For the stone color I basecoated everything first in black. After that was dry I did a heavy drybrushing of a medium gray. Then I did a lighter drybrush of pure white to hit the highest points and corners on the piece. Lastly I added bits of static grass and sand. All in all it took my about 4 hours to complete both pieces from start to finish.