Nicely done SBS flytire! That's a nice looking end result to boot. Like the others, I hadn't thought of pinking shears. I bet the craft stores will have a run on them since you shared this post!
Couple of other thoughts that you could do when making it would be to line the entire box with the craft store foam and then put slits in it from one end to the other. The end result would be a nice streamer box.
You could also get some of the adhesive magnet squares that are sold in Staples to put business cards on and place one on a portion of the box. The magnets are really nice for small flies like midge nymphs.