These are my instructions for preparing packaged corned beef, it
appears in the R.F.C. cookbook:

---= Corned Beef =---

Choose good grade of thin-cut corned beef (I prefer Nathan's).

Cook in the largest pot you own. Seriously, cook in lots of water.
First, rinse corned beef and and discard spices if present (old spices
were used up), or save spice packet if present. Start in cold water.
Bring to the boil (uncovered). Simmer 1/2 hour, dump water! Yes,
discarding water removes excess salt/nitrites. Okay, now the actual
cooking begins. Start in cold water (again? yes, again!). Add spice
packet (if none exists or since you dumped the first batch, add new
pickling spices. Bring to the boil, lower heat to low simmer. Simmer
aproximately 1 hour and add peeled carrots (whole) and unpeeled
potatoes (whole), bring to simmer again and add cabbage wedges. Simmer
til veggies are tender and remove. Continue simmering til corned beef
is tender yet firm; test with fork (your forking may vary). Remove
corned beef to roasting pan fat side up, cover liberally with brown
sugar, tent loosely with foil, and place in 325 F oven for 30-45
minutes. Remove corned beef from oven (now place veggies in oven to
reheat). Let corned beef rest uncovered 15 minutes. With sharp knife
slice thinly accross grain, and serve with veggies, mustard, and beer.
Getting ready:
http://i63.tinypic.com/20ie2oy.jpg
Beginning to simmer four pieces of flat cut corned beef, really
doesn't pay to cook less as corned beef cooks down to less than half
its starting weight and it requires several hours of cooking:
http://i64.tinypic.com/2wpuoh0.jpg