How difficult is it to make clean graphene?

If you're not looking for a perfect sample, pretty simple, the way it was discovered: with sticky tape and graphite.

https://en.wikipedia.org/wiki/Discovery_of_graphene

There are a few methods to make rhombohedral graphene (which demonstrates superconductivity at room temperature).

Normal carbon stacks into a hexagonal ABAB pattern.

For superconductivity, the layers need to be at least ABC (because twisted bilayer graphene does not demonstrate the effects (superconductivity, quantum hall effect) at room temperature FWIU).

Current process: CVD chemical vapor decomposition and then sort and stack graphene flakes.

Flash heating plastic yields graphene and hydrogen; but you must capture the flue.

There are new plastic recycling methods that intentionally don't produce graphene that maybe could produce more plastic and graphene.

But graphene is hazardous sort of like coal ash; so IIUC if you can make graphene onsite (e.g. from unsorted 'recycled' plastics) and lock it in to glass or another substrate that avoids transport risks.