I suppose that composing layered blocks is exactly what the beadmakers did, to create the beads shown. (Particularly the two longer more-recent beads, and Stefany's bead.)

Nevertheless, I would also assume that the manufacturer is a small industry, that is hand-work-driven, and small in output. These beads remain fairly rare.

Nevertheless, given the desire and the motivation—and cash support—an industry could be developed exactly as you suggest. And these beads could be cranked-out.

JDA.

P.S.—The artisans I know who work with Epoxy, and have good results, do not take any of the precautions/preparations mentioned here and above. They are more along the lines of mix/glue/wait. And they are happy with their results. As I said, I just don't have the knack for doing that successfully. So I don't do it.