1. Remove print and cardboard backing (if it's not cardboard, removing the backing).
2. Either measure the backing and then measure and cut your cork. OR lay the cork out, put the backing on top and mark with a sharpie pen. Then cut the cork.
3. Glue the cork to the backing. If it's cardboard simple Elmer's wood glue works well. You can use superglue as well. Do Not use hot glue.
4. Put heavy books or objects on the cork and let dry for several hours.
5. Once it's dry you can place the cork (cork side facing out) into the frame. Fasten it in (this depends on the frame design).
6. Now you can hang your new cork board!
Optional extras: Paint your frame, add stencils or other designs
Here's my frame before:
Here's my frame after: