I chose this (https://cdn.instructables.com/FX6/KDX0/J5SFZY4N/FX6KDX0J5SFZY4N.MEDIUM.jpg) to start with, then I created the outline with the hole.
Before starting it is always better to check how the CNC will behave.
When the piece is ready, use the acrylic varnish to paint the entire surface.
Acrylic varnish dries in 10 minutes but waits for one hour for safety.
Then you can use the sandpaper to remove the paint. I suggest you go to the largest grain (type 80), then go up to 180.
Only the outside paint will be removed, so the paint inside will remain!!! ;D
Now you can wash the Keychains with soap and water. Don’t worry, acrylic varnish is waterproof.
Just I finished, it was stolen from a friend! O_o