I use 2 part acrylic resin epoxy. 1:1 mix with mica powder to dye it.
I grab a picture of the patch (hopefully and svg). I do small edits in Carbide Create, for big edits I use inkscape.
Set up pockets and cutpaths in carbide create. My pockets at .15" deep. On 1/2" or 3/4" ply or MDF. I try to pocket out areas that are only 1 color with a border. Sometimes I have to add thin borders for the epoxy then cut out the border/barrier after it has cured to pour the next color (as I had to do between the blue and black in the item above).
MDF is flatter and seems to give a better cut without tear out. Ply is more durable and lightweight in comparison.
Nail on the hanging hardware.
I paint the painted areas and then spray a few coats of clear coat.
I mix the resin in clear plastic cups until clear then add the mica powder to dye (doesn’t take much, maybe 1/8 or less of a teaspoon.
Make sure your workpiece is level in both directions.
Pour in. I use plastic siringes or pipets to lay in the smaller areas. If you drip on the paint immediately wipe off with a paper towel.
I clean the siringes and pipets with acetone so I can reuse them a few times.
As the resin starts to set, I use a toothpick or nail to swirl it. The mica powder kind of settles and becomes 2-tone. You can buy a liquid dye instead but you use alot of it and it’s more expensive than the mica. I haven’t tried food coloring, or cement coloring.
Allow to cure and it’s done.