Place roast in crockpot. I use a 5 quart slow cooker.
Sprinkle roast with salt.
In a small bowl, stir together broth, vinegar, brown sugar, and Worcestershire sauce.
Pour the broth mixture around the roast.
Cover, and cook on low for 8-10 hours.
Shred beef with two forks, and return to crockpot.
Continue cooking for an additional 30-60 minutes.
Kosher salt - Kosher salt isn't as salty as table salt. I like to use it on roasts because it adds flavor without making the meat taste salty. Sea salt would be a good substitute. If you're using table salt, use half the amount of salt called for in the recipe.
Beef broth - Beef stock also works well. I like to use reduced-sodium beef broth.
Brown sugar - Light or dark brown sugar will work.
To freeze: Add everything to a freezer-safe container (I use a gallon freezer bag). Squeeze as much air out as possible. Then, you can freeze it for up to three months. When you're ready to use it, simply thaw in the fridge, and then cook as directed.