Zok,
Initially, I scratchbuilt the wood area right onto the base, then I made a very thick plaster mix, and poured it around the wood to give it that dug in look. Next some topsoil was added everywhere for the ground, followed by rail grasses. Then I added the spices (god this sounds like a cookbook recipie
). Once dry, I then started adding the baking soda, heavily on the outer edges, and getting lighter towards the back part of the dio. All of this of course was very messy to do, luckily I put newspaper on my bench for such undertakings. Some of the soil bled through a bit, but it helped blend everything together. A slight dusting of blue pastels here and there helped give it that tinted look.
"There you go with those negative waves again!"