I usually cook a brisket in the oven.
I buy a 15 pounder, or so, untrimmed. I rub it down with dry onion soup mix then put it in a large aluminum pan with 1/2 a red onion chopped up and a few cloves of garlic chopped up. I put in a tablespoon of vinegar and a 1/2 cup of water then cover it with foil.
Bake it at 290 for 5+ hours.
It helps if you let it sit overnight in the fridge with the rub on it. Comes out tender and delicious.