Large piston array bone meal farm

A large moss bone meal farm sitting on a 19 by 19 white stained glass platform. Two moss blocks at the bottom get bone mealed by dispensers, and 204 pistons driven by 216 observers sweep the moss growth off the stone around them. Stone brick stairs carry the drops down into a packed ice and soul sand line, which pushes everything through 26 composters on hoppers, and those composters turn the moss products back into bone meal for 24 chests while refilling the dispensers. It has to be primed once by hand and then it feeds itself. The build is 19 by 19 at the base and the tutorial takes about 22 minutes to follow. Java only, the creator says Bedrock does not work.

Bone meal the two moss blocks at the bottom by hand once before you switch it on. TheySix pins this and Palisades23 confirms the schematic does not start without it.
Put a stack of bone meal in the dispenser as well. An empty dispenser is the other reason people find the farm sitting still.
The whole build is done in creative with an auto placer, so observers and pistons go in at angles a survival player cannot reach. Expect to pause a lot and set temporary blocks to get the orientation right.
The farm is symmetrical, so if the pistons on one side do not fire, copy the working side across. That is how CalebTRBLX fixed his.
Turn it off once the chests fill up. amemil4965 filled his in a minute and the moss drops started despawning.
If the piston line with the obsidian does not move you lose most of the output and the farm stops feeding itself, franz5431 was down to a stack and a half an hour with that fault.