I really wanted to build a mirror frame for our master bathroom that had the look and feel of driftwood (so hot right now). I was pleasantly surprised at how easy this project was. I was especially happy about the fact it didn't require any nails or screws, just mounting tape.
I started with these pine boards that I treated with a concoction of vinegar and steel wool followed by a few coats of liming wax. See the post for a link to that process.
I replaced the outdated two smaller mirrors in the bathroom with one large one that was collecting dust in the basement. I attached the mirror to the wall with nothing but mirror adhesive.
I used my miter saw to cut four pieces for the mirror frame. I stuck the pieces directly to the mirror using outdoor mounting tape.
I added a piece of decorative molding to the top of the frame. The corners of that piece were adhered using wood glue.