There is a trick they used to do for decorative metal inlay where they would make sheet metal stencil, fasten that down and then hit the wood with a litte fork like dubus mounted in a drill press (think really agresive wire brush).
I don't know if this would work for you, but you're talking about such a small area....
If you only hava a couple of these to do, I'd carve them out with an Xacto knife.