How does rockwool work? Say I've got a cutting rooted in a 1.5" rockwool cube, now what? Do the slabs have holes in them to accept the 1.5" cubes? Right now I grow in 1 gallon grow bags. They're maybe 8" in diameter I think, but I only fill them about halfway because I only flood to 3" depth or so. I grow small bushes. What size cube/slab/whatever do I need? And what if I want an intermediate size? Are there blocks that take the 1" or 1.5" cubes, then plug into bigger blocks?