Even cutting 8.5X11 colored copy paper to 8.5 inch squares wasn't enough to make it look realistic because my box was just a hair bigger than 24". I ended up using nine 7.5" squares for each of the six sides: red, yellow, blue, orange, green, and white.
Then I used black spray paint to paint the edges and the grid. There's no need to waste all the paint on areas that will be completely covered with paper. Then I handed a couple students some fat glue sticks to cover the surface of each piece of paper one at a time, for me to place and rub down. I had to tack a couple corners down with hot glue, but it ended up being pretty smooth and the finished product has has a big enough wow factor that everyone who has walked into my room this last week has commented on it.
