To Make in the Slow Cooker: Place the roast in the insert and rub the taco seasoning over all sides of the meat. Top with the salsa and beefstock. Cook on LOW for 8 to 10 hours or on HIGH for 5 to 6 hours.
To Make in the Instant Pot: Cut up the chuck roast into 2×2 inch pieces. Add taco seasoning. Top with the salsa and beef stock. Cook at high pressure for 30 minutes.
Label a gallon-sized freezer bag. If making roast in instant pot, cut the roast into 2×2 inch pieces.Add the salsa and broth. Seal, squeezing out any excess air, and freeze.