Add the carrots and onions to one side of the beef, and the potatoes to the other side. (see notes)
Pour over the tomato sauce on top of the beef and vegetables.
Sprinkle the spaghetti seasoning over everything.
Cover and cook on HIGH for 6 hours WITHOUT opening the lid during the cooking time. (see notes)
Shred or cut the meat for serving.
Serve with the sauce from the slow cooker.
Enjoy!
Video
Notes
Jarred marinara can be used instead of a spaghetti packet and tomato sauce, though you will have to go heavy on salt, pepper, onion powder, garlic powder and oregano.
Store any leftover Italian beef in an airtight container and keep in the fridge for up to 4 days. Reheat over medium heat on the stovetop or in the microwave.
Instead of a chuck roast, you can use rump roast or bottom beef round roast. It should still yield fork-tender beef.