Place the brisket in a glass baking dish, fatty-side down.
Mix Montreal steak seasoning and red pepper flakes together in a small bowl; rub over the brisket firmly to press into the meat. Flip the brisket and continue seasoning the fatty side.
Stir beef stock, lemon juice, and liquid smoke together in the bowl; drizzle over the seasoned brisket. Cover the baking dish tightly with aluminum foil.
Roast in the preheated oven to your desired degree of doneness, or an internal temperature of 145 degrees F (65 degrees C) for medium, about 5 hours.
Remove from the oven, cover with a doubled sheet of aluminum foil, and allow to rest in a warm area 10 to 15 minutes before slicing.
