The factory tape player resides behind the flip-up door, so we'll remove this to make way for some accessories and controls.
Unscrew the factory tape player from the housing and you have a perfect spot to hide a switch panel.
Using superglue, glue the sides to the main panel to hold it in place.
From the front, we have a flat area for mounting. You could stop here but we want a completely integrated look and that requires a few more steps.
Use a jigsaw to cut the hole.
Drill two round holes for the level controls using a stepper bit (also called a unibit). Then, drill nine smaller holes in the right side to act as a grille for the navigation speaker.
Mix some Evercoat Metal Glaze on a small board using the amount of hardener shown. Do not use too much hardener.
Check that the piece fits one last time, and place the radar detector display in the panel to check that gap as well.
Let the primer dry for three to four hours, then sand it with 400-grit sandpaper. Use your finger to sand inside the holes for a smooth radiused look.