It would have been best to use 1/2" treated plywood, but I didn't have it, and I didn't want to deal with the weight. So I used what I had: 1/4" plywood, primed with Kilz Outdoor formula, and an outdoor latex on the front and an oil based paint on the backside.
To counter warping and give the sign visual weight, on the back of each panel I used 1"x3" boards at the top and 1"x2" boards along the sides and bottom - I left them long to act as the legs of the sign. Everything was glued and screwed in to make it sturdy. The top wood was bigger to accomodate the door hinges that I used. The stabilizers on the back were installed after I painted the front, and the back painted after the glue dried. A light-weight chain was attached to cup hooks on the inside angle, to keep the sign from splaying out too much.




After sketching everything out with pencil on the painted boards, I painted the store name in burgundy, similar to the highlight color of my shop. (The back-ground mild gray was similar in tone to my main interior color. This way, the sign strongly mimics the shop colors.)
The dark grey paint for the back of the boards I used on the front for body text, and for highlighting the arrow and word "GOLD". Since I was aiming for pedestrians, not car traffic, I designed for a more leisurely comprehension speed. But I made sure all the important information was there: services provided, hours of operation and phone number. The address was not important, so long as viewers knew which way to turn at the end of the alleyway.
Thank goodness I remembered to paint the arrow the correct direction for the back panel of the sign!
I learned from the first panel that standing over the sign to paint was a pain in the back. In my garage I have a stool on wheels, so I used that for the 2nd board - that's why it looks like I was painting at odd angles to the sign.
To give a feeling of completeness to the design, I sponged a border on each panel in the gold color that I painted the word "GOLD" and the arrow body color.
All in all, I did this in one day and four evenings, and spent just over $30 in materials that I didn't already own. Much better than the $120+ for just a commercial sign frame without even any graphics!
I'll post photos of the finished sign next time.