1. First make a very long cord of many colors to start off. To change colors, just knot the first color with the second and cut the ends short. Continue to mill it through. The knot usually will disappear within the cord.
2. Once you have a length you wish to work with, start at the bottom of a box side, draw a line of glue and glue the cord to it. Turn to the next side, add more glue and press the cord onto the glue. Continue in this manner until the entire box is covered.
3. When you have reached the top figure out how much yarn you still need to mill through and then knot the end off. Glue the end to the top of the box and cut the tail of the yarn away. If a little bit is still seen, tuck and glue it underneath the cord if necessary.