Looks nice

Cut your CP wood to shape and then tape your artwork in place.
Use a sharp pointy object and poke it through those '+'s on your art and into the wood base.

This example is on metal:

Then drill all your holes with a hole saw.
Once you have done all the holes, sand and paint your cp then stick your art down (if you want). You could just lay it under the plexi though.
Good luck.