Cut the beef into big chunks and boil it up in water. No need for salt but you might add some pepper, rosemary, a bay leaf or two.
Simmer the whole pot until the beef is tender, then add in the tatties...maybe some onions and carrots, too. Last thing in is the loosely cut-up cabbage, which doesn't take long to cook. Let it all simmer another 15 minutes or so.
Serve it with some lovely fresh soda bread and a pint of the black stuff. Corned beef and cabbage is not traditionally Irish--I also like to boil up a pot of colcannon--cabbage, tatties, bacon and some butter...maybe a little greens (like kale).
Boiling meat is popular in many rural cultures because you could use older and tougher meat.