Rinse the corned beef brisket under cold water
Place the brisket in the slow cooker fat side up
Add the seasoning packet if included
Add enough water, broth, or beer to cover the brisket about halfway
Add optional vegetables like onions, carrots, and potatoes around the brisket
Cover and cook on low for 8 to 10 hours
Cook on high for 4 to 5 hours if needed
Check that the brisket is fork-tender before removing
Let the brisket rest for 10 to 15 minutes before slicing
Slice against the grain
Serve with the cooking juices or strained broth