Let me say that I'm not so good in mechanics and consider what follow as a suggestion.

I used a thin galvanized sheet but I suggest instead to use aluminum that is more light.

The hole dimensions are the one I used for my switches and may vary depending on the ones you will use.

To have a better aesthetics I used a simple image put on an adhesive plastic sheet printed on a color laser printer. The image I used is

Obviously you are free to design your own and if you would like to share your panel with us drop me an e-mail with the file: I will put a link on this page.