Line a shallow roasting pan with aluminum foil. Place the brisket on the foil. Stir together the steak sauce, liquid smoke, and ketchup. Pour half of the mixture over the brisket, then turn the meat over, and pour sauce over the other side. Wrap tightly in a double layer of aluminum foil. Refrigerate for at least 24 hours.
Preheat the oven to 250 degrees F (120 degrees C). Let the roast stand at room temperature while the oven preheats to take off some of the chill.
Bake for 6 or 7 hours in the preheated oven. You can leave it in even longer if you turn the oven down to 200 degrees F (95 degrees C). Remove brisket from the oven, and slice across the grain. Return to the roasting pan, and serve with sauce.