This seems usefull, though it might be better to also have other versions like one with 2 exposed slime faces, or be able to choose which faces are sticky and which aren't (though this might be hard to fit into the block data since that's only 4 bits)
I like this! It's clever and, surprisingly, original! Though I do think it should only require 5 wood blocks, given that only 5 sides of the blocks are covered by the wood (and technically 99% of the wood involved is wasted already since only a very thin layer of wood is actually used).
also i would suggest a trap door design for the sides instead of simple wood or slime stained wood.
with slime blocks and trap doors already being transparent, it would look fairly nice, to see the usual slime interior through the sides of the trap door texture.
another whacky idea would be to have the different types of wood give you differen types of boxed slime boxes. this way you could easily mark special blocks while building or build different colored lines/paths of boxed slime blocks. they can still connect to each other, it would be *only* a graphical thing.
Hmm, that might indeed work better. Unfortunately i'm really not that good with renders.
That could be useful... though Mojang seems very reluctant to give us different colored wood items.