Lie one side of your lampshade frame or completed lampshade on top of the styrene. Trace the lampshade's shape onto the styrene and cut out the shape.
Remove the backing from the styrene and press it to the inside of your lampshade or the back side of the fabric if you are using self-stick styrene. If you are using plain styrene, use fabric glue or a hot glue gun for application.
Cut the fabric around the styrene if you are making a new lampshade. Trim any excess styrene if you are lining an existing lampshade.
Secure the styrene with clothespins, and allow it to dry for 20 minutes. If you are making a new lampshade, delay this step until you have attached the fabric and styrene to the frame.