I find it a bit disappointing that many of the cool biome specific items are complete dead ends crafting-wise.

In particular, all you can do will Chunk of Flesh from the Flesh Biome, is craft it into a Block of Flesh.
It would be nice if there were something you can do with it.

I would suggest as a starting point that creating it on its own as a 1x1 unshaped recipe should yield vanilla rotten flesh.
Possibily Chunk of Flesh should be edible on its own to give a similar effect to rotten flesh.

Closing this because we either can't/won't fix it or it's not an issue in 1.13

I'd say there's a lot of room for, say, a magic mod, to work with the various BoP materials -- besides the Nether stuff, there's all those gems and new plants.