Preheat the oven to 325°F
Remove the corned beef brisket from the package
Rinse the brisket under cold water
Pat the brisket dry with paper towels
Place the brisket fat-side up in a roasting pan
Add the spice packet if included
Add 1 to 2 cups of water, beef broth, or a mix of both to the pan
Cover the pan tightly with a lid or heavy-duty foil
Bake for about 3 to 4 hours, or until tender
Check for tenderness with a fork
Remove the foil during the last 15 to 20 minutes if you want a browned top
Let the brisket rest for 15 to 20 minutes
Slice the brisket against the grain
Serve warm