Here is how we made them:
#1- We purchased unpainted open back frames from Michael's Arts and Crafts (with our 40% off coupon of course) and then painted and sealed them with our desired colors.
#2- We cut out a piece of solid cardboard to fit in the back of the open frame and proceeded to hot glue the corks onto the cardboard in our desired patterns. (My mom donated some wine corks she found at a yard sale and the rest we purchased on eBay.) Notice in the picture below that the frame is not painted... we used it as a guide while the others were drying but do not glue all your corks down until the frame is painted and ready to go because you will not be able to get the cardboard with the corks attached in or out after they are all glued on.