Rinse the corned beef brisket under cold water
Place the brisket in a large pot or Dutch oven
Add enough water to cover the brisket
Add the seasoning packet if included
Bring to a boil
Reduce to a low simmer
Cover the pot
Simmer for 2.5 to 3.5 hours, until tender
Add vegetables like potatoes, carrots, and cabbage during the last 30 to 45 minutes if desired
Check that the brisket is fork-tender
Remove the brisket from the pot
Let it rest for 10 to 15 minutes
Slice against the grain
Serve hot