That doesn't sound like a bad idea for a material... Then just form your stack out of foam, paint the surface a similar base shade, and start gluing it down. In fact, you could roll it around in the material while the paint is still wet. And to make it realistic, just put little loose piles round it in certain spots, and use matt medium to hold it down. Woodland Scenics has a Harvest Gold field grass also, which you could cut up.
Dave
Los Angeles, CA
-DPDP Model Accessories-
http://eje.railfan.net/dpdp/