First, I cut the flaps and top off of a box to fit the cabinet. Then, I cut a piece of fabric so that it would just cover the front of the box that would be showing.
I hot-glued the fabric down along the edges and viola!
You would never know it was just a regular old box unless you pulled it out of its space. Of course, if more of your box was going to be visible you could always glue fabric inside and all around. This project probably cost me less than $1 and I'm very happy with the results!
I hope everyone had a fun and relaxing Labor Day holiday!