The magic of magnets.
The display is a Buck counter display with rear storage. It has white plastic back (behind the knives) channels for shelves ordinarily.
I picked up a sheet of tin for HVAC ducting, cut it to size, covered it with red felt, and glued it in place.
A couple of .25" magnets on each knife and viola!
Unfortunately, my 303 collection has outgrown the case so I need to come up with something different now.