These are some simple yet effective things to make your own base using foam, cement and paint.
I. making the terrain:
-conceptualize your contour
-cut or shape your terrain
-cover it with cement
-while the cement is damp, puncture it using your fingers to make "dimples" on your terrain.
-sprinkle some cement on your terrain. this make's the rough texture. then spray a a little bit of water.
-let it dry
-coat it with primer or some flat coat.
II. Painting the terrain
to make it look natural, we'll use watercolor or just use acrylic paint and dillute it on water.
-just apply it on the terrain preferably at the topmost part of the terrain and let it run on the grooves.
-use yellow paint first, then red, then some orange, then a bit of black on the dimples.
-let it dry and topcoat it.