I primed the pieces with an Army Painter black rattle can.
The inside I painted a dark brown, the rim with the same mid brown as the rest of this SiFi terrain set.
To create the parched ground effect, I used diatomaceous earth, mixed with watered down PVA glue. I saw this technique on the TWS YouTube Channel and wanted to give it a try for some time. The price gets much cheaper when you buy bigger bags, but for a first try I went with a smaller box.
Diatomaceous earth comes in different colors, by chance I bought a brown one, I think I might stick with that color.