I use synthetic chamois you can get at any auto parts store. I cut an appropriate-sized piece for the knife height (so the stones and strops don’t drag and cross-contaminate), wet it, and wrap it around the spine. The jaws compress the cloth as they are tightened on the blade, and any gap between jaw and FFG blade is automatically filled in by the cloth and the blade stays centered effortlessly.
The coefficient of friction is quite high when damp and remains very high after the chamois dries. Additionally, it becomes very stiff. The knife don’t move!
Reusable almost infinitely. Rewet, brush off, and clamp again.
I’ll post a pic later tonight.
***No chamois were harmed in the sharpening of my knives–only me…