You need four sheets of foam core with cutting tools for the foam core (I used mostly an X-Acto Knife and my cutting mat), glue gun and/or Elmer's school glue, LED Light Strip: Lighting EVER Lampux 12V Flexible LED Strip Lights, LED Tape, Daylight White, 300 Units 3528 LEDs, Non-waterproof, Light Strips, Pack of 5M, Power Supply for lights: Lighting EVER® Power Adaptor, Transformers, Power Supply For LED Strip, 12V, 3A Max, 36 Watt Max (both available from Amazon.com), and 2 sheets of Lexan or Plexiglass or the like (available from Lowe's or Home Depot or Ace Hardware)
There was not much foam board left but this is what I need to make a ruler for my quilt.
Here is my light box. I made mine bigger than the one on YouTube. They suggested using an 11 by 14 inch sheet of the Lexan or Plexiglass. I used 18 inched by 24 inch sheets. Instead of making mine 4.5 inches tall as in the original plans. I made mine 2.875 inches tall.
Here is a side view of it sitting on my mother's couch showing the power supply. The dimensions are approximately 2.875 by 18.75 by 24.75. You are supposed to sand the edges to neaten it up. I am happy with it as it stands. I may add some tape around the top edge to secure the Lexan. One of my sheets is a quarter in thick and the other is only an eighth of an inch thick. The quarter inch thick piece I already had on hand. I had been using it on top of under-counter fluorescent lights to make a light box. That one worked well enough but I had three separate cords to plug into the wall. Now I only have one. I should also mention that I used a piece of freezer paper between the sheets of Lexan to act as a diffuser. The video was using a piece of foam board that had had the paper removed. I tested the foam board that I was using and the paper did not come off easily. I abandoned that notion and substituted the freezer paper. I also used the 18 inch wide aluminum foil to wrap the piece of foam board upon which I secured the led lights.
I should mention that I was a bit careless with the glue gun when I assembled the light box. I was gluing the sides to the base and some glue leaked out of the corner where the edges meet. I burned my pinky badly. A cautionary tale....please be careful when using glue guns. Use some common sense and anticipate that when you push things together the glue could ooze out.