I made these C Clamp Holder Racks for my Dad as a Christmas present.
I used Fusion 360 to create a model with slots that would allow the top portion of the clamp to be easily placed and securely indexed to prevent them from falling off. I then used my CNC to mill the parts out of some scrap cherry I had left over from another project. Mounting holes were drilled and a wider diameter hole was added to hide the screw heads.
A 45-degree chamfer was cut off the bottom edge on the front to provide clearance for the smaller clamps on the left-hand rack and create a more finished look overall. Finished with two coats of brush on poly, sanding between coats with 400 grit.