Recipe for the base I use on my Silver Templar army; based on original Darren Latham recipe.
It can be used for many 40K and AoS army

1. Glue some rocks or slate pieces directly on the plastic base with superglue
2. Base coat the entire base with Steel Legion Drab to work as foundation for the next steps
3. Apply texture Stirland Mud all over the base leaving the rocks exposed
4. Drybrush with Balor Brown
5. Paint the rocks with Mechanicus Standard Grey
6. Shade only the rocks with Agrax Earthshade
7. Drybrush all over the texture and rocks with Karak Stone
8. Drybrush gently all over with Screaming Skull
9. Complete the base by painting the rim with Steel Legion Drab