You don't slow cook a burger. The mistake most folks make with their homemade burgers is getting the meat patty too thick. You don't want the patty to be more than one-half inch thick, thinner would be better. I put my hamburger in a big bowl and mix in the seasonings before cooking. A little salt and more black pepper is all you really need, but you can season it as you prefer.
Some folks add finely chopped onion.
I sometimes mix in a handful of crushed corn chips for a different flavor and texture. If you have the little buns about the size of a hockey puck the ball of meat will of course be smaller than if you are using a plate-size bun. Best way to form the ball into a patty is to put it between two sheets of wax paper or plastic wrap. You can smush it out with your fingers or use a rolling pin on it. It doesn't have to be perfectly round unless you have some sort of compulsive disorder.