I fell in love with these gallery frames at my local frame shop, but they're a little pricey. So I deconstructed them and figured out their secret.
A corrugated sheet in between the two mats makes them stand out in the frame and showcase the artwork.
Choose a mat that will fit your art piece and mount the art normally onto the mat.
For the second mat, choose one that will fit the frame that you want to end up with. Then, trace both the inside and outside edge of that mat onto a piece of corrugated cardboard.
Once you've traced them, measure back a half an inch from the inner edge.
You want to make that opening bigger than the actual opening so you can't see the cardobard when the frame is in place.
Now, layer your art and mats into the frame. You want the bigger mat on the glass and then the smaller one behind it.
Put the backing in place and your frame is set to go! Love it! I'm Mrs. Fixit and it's just that simple!