Buy a large brisket, marinated in spices & sealed if you can find one. If not, then soak the plain one overnight in water with ¼ cup vinegar & 1 teaspoon pickling spices. Drain off water & rinse off spices.
Place on rack in a large pan (I use electric skillet most of the time) and cover completely with water. Bring just to a simmer & cook several hours. If you cook in oven it should not be above 300.
If you boil the meat will be tough. I trim off most of the fat, but the broth should be saved if you want to make corned beef & cabbage.
When meat is fork tender, cool and place on cutting board. With a very sharp knife (the big butcher knife Mike's family gave me is perfect) slice as thin as possible across the grain. The meat shrinks a lot, but a big brisket makes a lot of meat.