The process is likely obvious, but here's a hint:
I used a mini pack and rolled a small amount into a cylinder about 1/4in in diameter and 1/2in long. I then pressed one end to make a teardrop shape, where the wide part was thinner than the tapered part.
I wrapped the wide part all the way around the cord, sealing the tear in the sheath. I then curled the remaining, thicker, tapered part around another piece of the cord to form the shape. I removed the cord because I wasn't sure if it would stick or not, and then bent the molded piece back as close as possible, knowing that it would flex a little once dry.
I also took the opportunity to reinforce the cord where it comes out of the charger.
Now I can wrap the cord around the wall wart and secure it to itself- a feature found on many cords, but not mine.