Place corned beef in slow cooker fat side up. Sprinkle spices over the corned beef. Add enough water to just cover the corned beef.
Cook on high for 4-5 hours or on low 8-9 hours.
If you want, you can easily add baby carrots to the slow cooker as well. Add them with the potatoes If you also want to add cabbage, add it in the last 30-45 minutes so it has time to wilt but will not entirely disintegrate like it would if you added it in the beginning.