You can see the materials the base was made from – namely sand, multi-purpose filler to create the dunes, red oxide paste to cover gaps, and chipped wood pieces (in this case taken from the local park):
In order to ensure it would look warm, it was undercoated white:
To paint the sand, these were the paints used:
Basecoat tank-brown, then drybrush: 1) flat-earth 2) plague brown 3) zamesi desert 4) ushabti bone. Glaze with smoke to finish – then dust with pigments. I made a previous tutorial on how to do this here.
Crackle paste was used to create the dry river-bed effect:
I forgot to take step-by-step photos of this; but it was Decoart paste, which you apply with a spatula (or something similar), leave to dry, then paint over. It was then brushed with pigments, to create the dusty effect.