Spray a 6 to 7 quarter slow cooker with nonstick cooking spray. Carefully remove the corned beef from it's packaging and set spice packet aside (we will be using that later). Pat corned beef dry with paper towels.
Place onion quarters or pieces in the bottom of the slow cooker. Add the corned beef (fat side up) on top of the onions and then sprinkle with the contents of the spice packet (that came with the corned beef).
1 onion, 3 to 5 pound corned beef brisket
Put the bay leaves and crushed garlic on top of the corned beef. Add the potatoes and carrots to the slow cooker placing them around the corned beef.
2 bay leaves, 3 cloves garlic, 2 to 3 large carrots, 1 pound creamer potatoes
Carefully add the chicken (or beef) broth, pouring over the top of the vegetables.
2 ½ cups low-sodium chicken broth
Cook on low for 6 hours.
Add the cabbage wedges to the slow cooker and continue cooking on low for another 2 to 3 hours or until the corned beef is tender.
1 small green cabbage
Gently remove the corned beef from the slow cooker and let rest for 10 to 15 minutes before slicing thinly against the grain.