You pinch your strands of yarn together, then wrap your thread in the center of the hook. Youtube "glo bugs"... that should explain how you tie it with a vise.
It depends. I'd like to tie mine with a vise, but I usually forget to do it before I go. If I'm on the water and I remember to bring the "magic thread", then I'll tie it and trim it there. I usually run the hook through the ball, and slide it up. If I have an egg loop tied on, I can secure the yarn and the roe with the loop. Sometimes I just run the yarn with some scent on it.
Hands down, I only like to do mine in a vise at home directly onto the hook. They're quick and easy and I can tie up a 46 pack of hooks in about an hour. I don't use bait often, and never with a yarnball so an egg loop isn't needed.
You pinch your strands of yarn together, then wrap your thread in the center of the hook. Youtube "glo bugs"... that should explain how you tie it with a vise.