Rinse brisket under cold water and pat dry.

Layer sliced onions and garlic in the bottom of the slow cooker.

Place brisket fat side up on top of onions.

Sprinkle spice packet or pickling spices, peppercorns, and bay leaves.

Add carrots and potatoes around the brisket.

Pour in broth or water until brisket is mostly covered.

Cover and cook on low 8–10 hours or high 4–6 hours.

Add cabbage during the last hour of cooking.

Let brisket rest 10 minutes before slicing against the grain.

Serve with vegetables and spoon over cooking liquid.