Coat the inside of an oven roasting bag with flour. Place brisket inside of bag. Pour liquid smoke over the brisket and sprinkle on garlic powder, dry onion soup mix, and ground black pepper. Seal bag. Using a fork, make two sets of holes in the top of the roasting bag.
Lay bag in a broiling pan. Bake in a preheated oven for 6 to 8 hours.
