Craters and texturing with sand

1. Start with a proper base

2. To form the crater shape use a spackle (US) or polyfilla (UK), the latter being actually better as it is cellulose-based and does not shrink or warp while drying. Note that my projects that involve a lot of water-based spackling paste are usually constructed on a plywood base to prevent warping

3. Cover the whole thing with a PVA glue and sprinkle with fine sand:

Unpainted crater

4. When it is all dry, shake off excessive sand

5. Spray it all with a black paint

6. Drybrush it all with a grey paint

7. Glue some static grass to the base's rim

8. Blend the line between grass and sand with some black paint