To flush out some of the sodium from the corned beef brisket, place the brisket in a large stockpot and cover it with cold water. The water should be a couple of inches higher than the meat. Place the pot on the stove, cover it and heat it on high, just until the water boils.
When the water boils, turn off the heat and carefully transfer the corned beef to a platter. Drain the water from your pot.
Place the corned beef back in your pot and cover the beef with hot water, until the water is about three inches higher than the meat. Add the contents of the seasoning packet to the pot and cover it. Heat the pot on high, and when the water boils, lower the heat to let the pot simmer.
Simmer the corned beef, covered, for 50 minutes per pound, until it's fork tender. (It should take 2.5 hours for a 3-pound brisket.)
When it is tender, carefully transfer the beef to a clean platter and keep the cooking liquid for now. Let the corned beef cool off at room temperature for 15 minutes before slicing it thinly against the grain. (Slice the meat on the diagonal in the opposite direction of the flow of lines in the meat.) Pour a little of the cooking liquid over the meat, but note the liquid will be salty, so don't use too much. Reserve some of the cooking liquid in a small covered container to use as needed.
Store the leftovers in a sealed container in the refrigerator for up to four days.
Notes
The seasoning packet comes in the package of corned beef. The packet usually contains peppercorns, mustard seeds and bits of bay leaf.
The sodium listed in the nutrition information is an estimate, based on briefly boiling the corned beef first to flush out some of the sodium.