After feeling comfortable with the cutout I planned, I drilled holes on the inside corner areas. I do that because when cutting out the material the cutoff blade on the dremmel tool will not cut a sharp corner and leave a nice radius where the corner will be.
The process is unexciting....just cut close to the lines and leave a little for finishing. So I made all the cuts after drilling the corners. Then using files and sanding drums I finished the edges on the cutouts.