How to do it:
Arrange a few dried leaves on a blank photo mat securing in place with small pieces of tape. Alternately, you can arrange the leaves while they’re still fresh. Fold over to the backside of the mat and secure with tape. The leaves will dry in place and wrap nicely to form a clean edge.
More ideas:
Try using other natural elements such as birch bark, pine needles or twigs to create a seasonal mat.