I told myself "hit the box with a flat base, do not go on edge." As I approached it, I tried to keep my speed low and was going moderately slow when I decided to shed more speed... on the take off ramp. I landed on my toe edge and it instantly went out from under me, causing my right shin to scrape painfully down the box.
The scrape is about 3 - 4 inches long and has left part of my shin completely numb 3 days after teh fall. I think I'm done with boxes for this season.