Step 1: Supplies
Step 2: Design
The outer box will be made out of Black Foam-core. it will have the heart cut out on top and the wax paper glued into the inside.
Inside heart will have boning around the symbol. I chose to make it out of white foam core, but you may want to use black and line the insides with aluminum foil (you can also use white and foil to increase the brightness, and maybe create a less pix-elated version.
In-between the heart, and the back lid will be the LEDs. This will let you sandwich the pixels instead of having to glue in each one.
The back lid will be made of black foam-core to give the outside an all black look.
To create the stencil I took the White symbol inverted the colors, and cut it in half. When cut in half it would nice print on a 11 X 17 sheet of paper. (I am not sure if the full symbol was the one I finally used.)