Thanks, Grub. Welcome to the forum!
The 2nd version of the bases (the primed ones) are more successful. Basically, you lay some cork down to build up the irregularities in the soil because forests are not flat. Then I glued the receiver bases for the Woodland Scenics plastic trees where I wanted them. Then I made a slurry of glue, rubbing alcohol, water, sawdust, potting soil, sand, tile grout, gesso, and clump foliage. That mixture was spread over the whole base and used to blend in the fallen logs (broken sticks from my yard) and the resin tree stumps I ordered from Green Stuff World. After that, prime it with rattle cans. Paint it how you like, sprinkle more potting soil on, and add a liberal amount of leaf litter. The Moss is ground up green tea from the dollar store.
This video gave me a lot of the concepts and got me started: https://youtu.be/ToF1Do_HPag