A 3-pound brisket typically takes approximately three hours to cook on the stovetop or in a 325-degree oven. Cook brisket in a slow cooker for six to seven hours on high or 12 to 14 hours on low. Add extra time for larger briskets or to reach the desired tenderness.
Bon Appetit recommends not trimming too much fat from the brisket and cooking brisket in the oven, which has more even heating than the stovetop. Leaving some of the fat provides moister, more flavorful meat. When using a slow cooker to make brisket, sear the exterior of the meat on the stovetop first to add deep flavor and rich color to the meat.