To make the fingernails, slice the two sides of the fingernail, then straight across the top. Then make a slight curved slice for the bottom nail bed. Next, take your knife and carefully slice the fingernail piece off the top. See the below photo in the blog post for sizing to see how big you want to make your nail.
Next, to make the knuckles, make one slit along the middle with two crescent slits directly above and below it. Then halfway between the new knuckle and the nail, make two crescent slits. And add two more crescent-shaped slits at the very bottom.
Boil the hot dogs for 4-5 minutes.
Then place each "finger" into a hot dog bun loaded with ketchup - be sure to smear some ketchup on the bottom of each "severed finger" and a bit at the top of the bun.
If you want, you can add a thinly sliced square piece of white onion for the "nail," but it's a bit of extra work that I didn't think was needed.