I’ve been experimenting a bit more based on A Longworth center finder.
There are pre-made material that you can cut away, but this gives a lot more flexibility and you can cut instead of engrave to remove material.
This is my final test run to make sure everything came out OK. Thanks to @Squid for pointing out “greyboard/chipboard” for mock-ups. The finished product will be two different colors of acrylic.