Layer onions and garlic at the bottom of the slow cooker.
Place brisket on top, sprinkle with spice packet.
Pour water until beef is nearly covered.
Cover and cook on LOW for 8–10 hours.
After 3 hours, add potatoes and carrots.
Two hours before done, add cabbage wedges.
Let beef rest 15 minutes, slice against the grain, and serve with vegetables and broth.
