Here's a little Behind the Scenes How To ...
QUICK TIP: Foam core is paper glued to stiff foam glued to paper. If you carefully cut through just the paper on one side, position the cut along the edge of a table and press down firmly you can create a 90 degree angle, making two sides for your box with one piece of board.
I then cut a piece that was the width of the box and half the height. This provides stability – also known as keeping the box from collapsing on itself – and allows me to "hang" backdrops (in this case a piece of handmade paper) using tape or bulldog clips.
(SAFETY NOTE: Please don't put your light source right against whatever translucent material you choose. That would be a fire hazard.)