Fill a shadow box frame with dark velvet and natural elements for a modern look.
The Martha Stewart Show, October 2010
Remove mat from frame. Cut a piece of cardboard 2 inches smaller in length and width than the frame mat. Place cardboard on the wrong side of velvet; trim velvet so it extends 1 1/2 inches from each side of cardboard.
Snip an arch shape from each corner of velvet. Fold two opposing sides of velvet in toward center, and tape to the back of the cardboard. Tucking in corners, fold and tape remaining two sides to back of cardboard.
Cut a piece of cardboard 1 inch smaller in length and width than first piece. Attach this piece to the center back of the velvet-covered board with hot glue.
Arrange shells as desired on the velvet. Secure shells to velvet with hot glue. Center board on top of frame mat and glue in place; place mat with board in frame.