I’ve been on a wild tear adding french cleats to my workshop and garage walls. I’ve been experimenting with various designs and have pretty much settled on this design for mounting dowels (1/4" and 5/16").
Here’s a file with holes for both size dowels…
You can easily fit eight of these on a single sheet of plywood.
BTW, this is one of those rare cases that I recommend using cheap 1/8" ply from the big box store – “GoofGrade” makes this project quite inexpensive – I can knock out 8 holders for ~$3.50 and 30 minutes of cutting.
Use at your own risk. Not for commercial use or resale.