Tier-3 workshops are the pinnacle of my current innovation in double-knitting. They represent the most esoteric techniques, and while some (like some in Tier 2) require only Foundations-level double-knitting knowledge, the attendant single-layer knowledge is more advanced. And some, of course, build directly from Tier-2 workshops to further expand those techniques.
As always, pay attention to the prerequisites! I'd rather that you wait to take a workshop you really want, instead of having a bad experience because you didn't have the appropriate skills to build this next tier on top.
Tier-3 workshops include: