Twelve sheep wool farm

A twelve sheep wool farm, rebuilt by Voltrox from ianxofour's design. The sheep sit in individual glass and leaf boxes over grass, and when one eats the grass the block update runs a redstone torch and piston clock that fires two dispensers full of shears across the whole array. Wool drops through to a hopper and one chest. The leaves are structural rather than decorative, because light has to reach the grass for it to grow back. It is a fixed size build, not a modular one, and the whole thing costs about two stacks of leaves and dirt.

Corner sheep not getting sheared is the most reported problem by far. RizzyPanda6 says only some sheep shear on each pass but all of them get done eventually, and the cases where they never do trace back to trapdoors placed wrong.
calmc warns the sheep are miserable to get into the boxes, jumping and clipping up through the trapdoors into the ceiling. bazookabullet101 found they can only escape if you break the dirt above the glass after pistoning it.
Use a dispenser in the middle, not a dropper. animaediamond catches this on several people whose farm does nothing.
The leaves have a job. richardyok4026 points out light passes through them to the grass, so swapping them for a solid block stops the grass growing back.
Shears wear out. LQ_duck replaces them about every ten Minecraft days, so it is not fully hands off.
It does not work on Bedrock. Bankrupt-z7g says you cannot even click the redstone there, and Sl1ppin confirms after building it.