I remixed here DustBunny67's amazing “Sharpening Guide”, hoping to improve it in some areas:

• first of all, my diamond plate did not fit, so the base plate dimensions were changed to accomodate a 20x7x4 cm sharpening plate or stone
• Increased the overhang areas of the clamps, so that they can stabilize the chisel in a better way (better grip on the edges)
• removed some geometry related to the size increase of the base plate

Do yourself a favor, and print the clamps with ABS or PETG filament, otherwise they will not hold your chisel in place safely. PLA pressing against PLA is to slippy. You might also want to consider sanding down the lower surface of the clamps, until it matches your chisel thickness. Alternatively, you can add a modifier in your slicer, insead of the sanding precedure, so that you increase the thickness of the clamp overhang. This will add additional pressure from the top, and the object to be sharpened will be fixed to the sled.