Your knife will slice thru it like butter. (as long as its sharp)

You can just trim out some ledges for the frogs to climb and perch on and I usually do a few angled for top to bottom crevasses for the appearance of where water carved the land away.

You don't have to do a lot of them just remember to exaggerate the cuts since the silicone will fill a lot of the cuts in.

You could just have the wood in place and propped up with stones or other pieces of wood thats atop the substrate if you think you will be needing to remove them often.

Looks great so far Kisa