I normally do paper cutting once a week, and I became interested in making paper light boxes. I had the design, but I was hesitant to try it. Just then, I happened to see the LED strip contest so I hurried to make my first LED light box.

Supplies

Cutting Mat
Paper Cutting Knife (I used NT cutter)
160~190gsm Paper
2~4 Foam Boards (preferably thicker than 3T)
Double Sided Tape
Led Light Strip
Led Controller
Battery Pack
Glass/Plastic Film/Vinyl
(if you want to protect the interior)
Ruler
Cardboard Box
Glue

Step 1: Designing & Cutting

Design your template. Draw what you want and divide the parts to layers. Remember to always have a 1~2cm frame on the outer edge. I used A4 paper. Also, have a blank paper with no design to place behind so that the LED won't show directly, and to spread the light more widely and give it a natural look.

Step 2: Make a Frame (Spacer)

Now that you have finished the hard part, review your work and see if there is any fluffy paper that you haven't removed or some minor errors. Then, cut the foam board to 1~2cm sticks and tape/glue them onto the frame part on your template. It is fine if your frame part is ripped or messy since you will stack them up all together.
*The foam board not only works as a supporting structure, but also a spacer, which amplifies the beauty of the light box. I suggest at least 5T.

Step 3: LED Lighting

Now, add the led strips to the back of the light box. Adjust the position of the strip and the battery pack so that it looks nice and clean. Remeber to put in the blank paper mentioned on Step 1. Make sure the LED goes through at least 2 layers of paper for a smoother look. Connect the led strip to the controller and connect the controller to the battery. Make a slight ditch on the cardboard for the wires and the led strip to settle inside.

Step 4: Make a Box

You can use a shoebox or any kind of box and decorate it, but if you don't have one that perfectly fits your template, just make one with the foam board or the cardboard. The foam board frame that you made on the previous step would be sturdy enough, so you won't have to make a box that sturdy. Glue the frames to the box if necessary. Remember to make room for your LED light strip and the battery pack/wire. There are no specific measures for this because the thickness of the box will depend on the number of layers of your design and the thickness of the foamboard and tape/glue that you used. Use tape for extra support.

Step 5: Make a Cover

I used a plastic film to cover the front part. Tape it tightly on the edges.

Step 6: Apply Paint

Apply spray paint all over except the front film. Cover it with paper and tape. Use masking tape if you have it. I used a useless piece of hard paper and tape for covering up. Spray and let dry for 10minutes. Do this multiple times for a smooth surface. I managed the front side with paper because the masking tape fell of while spraying.