Slowly pour beef stock into pot around the meat making sure not to disturb the salt and pepper on the roast.
Cook covered for 8 hours on the low setting (or 5 hours on high.)
Remove lid and test meat. It should be tender enough to pull apart with two forks.
Remove roast from pot to a large plate or platter.
Remove fat from meat, discard fat.
Shred the meat by using two forks to pull the meat apart.
Let meat cool, label freezer bags and fill with the desired amount of meat (see note #1). Remove all air from bags, lay flat and seal.
Place bags flat in freezer for future use.
Notes
Freeze the meat in portion sizes based on how you are going to use the meat. Sandwiches require more meat than casseroles, burritos, pastas and salads.