I've begun creating some new terrain pieces for my large table (4'x6'). While I have several city blocks built for this table, after a while it starts to get a bit boring using ruins every game. The terrain I've built for Malifaux works fine on the smaller tables, however when spread out on a larger table it tends to look a bit sparse.
I began by cutting green foam with a hot wire cutter. This is the easiest way to create rock formations that resemble something you'd see in the American west. Simply move the cutter in and out to create the striations in the rock face. Once these are cut and shaped, I mount them to MDF with wood glue.
To match the texture of the table I use a textured wallpaper as a base. This gives an interesting look without creating so much texture that models won't stand properly. Around the edges of the rock formations I used wood filler to createdebris piles where material would naturally collect. One the shape has been built up a give it a good coat of wood glue and cover it with a mixture of kitty litter and sand.
After that has dried overnight shake off the sand and use a dust whisk of soft bristly brush to knock off any loose material that didn't come off when you shook it.
I like to use Behr paint and primer for terrain projects. They can color match any of you model colors and have a good selection of the board. For desert terrain I like to use a terracotta color as a base. This can then be dry brushed with a light brown and cream to mimic the formations you find in the American west.
To finish off the project I like to apply some lichen and dead looking tall grass to areas that scrub may take hold. I use Tacky Glue or Super Glue for this. Either product with hold the material in place, but I've found that Super Glue dries faster and leads to better results for the tall grass. After everything is dry I spray it with Krylon Low Odor matte finish. This gives a durable coating that doesn't look glossy.