Place the sliced onions and minced garlic in the bottom of your slow cooker.

Season the beef chuck roast all over with salt, pepper, thyme, rosemary, oregano, and onion powder. Place the roast on top of the onions in the slow cooker.

Pour in beef broth, soy sauce, Worcestershire sauce, and balsamic vinegar over the beef.

Cover and cook on LOW for 8-9 hours, or on HIGH for 4-5 hours, until the beef is fall-apart tender.

Remove the beef from the slow cooker and shred it using two forks. Discard any excess fat. Return the shredded beef to the slow cooker and stir to coat with the juices.

Preheat your broiler. Split the rolls, butter if desired, and place on a baking sheet. Broil for 1-2 minutes until golden.

Pile shredded beef onto the toasted rolls, top with provolone cheese, and broil again for 1-2 minutes until cheese melts.

Ladle the hot au jus into small bowls for dipping and serve the sandwiches immediately.