01 - Scatter the thinly sliced onion and minced garlic across the bottom of a 6–8 quart slow cooker.
02 - Season the beef chuck roast with black pepper on all sides, then place it directly on top of the onion and garlic bed.
03 - In a mixing bowl, whisk together the beef broth, soy sauce, Worcestershire sauce, dried thyme, dried rosemary, and bay leaf. Pour the mixture evenly over the roast.
04 - Cover the slow cooker and cook on the low setting for 8 hours, or until the beef is fork-tender and pulls apart with minimal effort.
05 - Transfer the beef to a cutting board and shred using two forks, discarding any large pieces of excess fat. Remove and discard the bay leaf from the cooking liquid, then strain the liquid into small individual bowls for dipping.
06 - Preheat the oven broiler. Arrange the French rolls on a baking sheet, layer each with shredded beef, and top with a slice of provolone or Swiss cheese. Broil for 1–2 minutes until the cheese melts and the rolls are lightly toasted.
07 - Serve the hot sandwiches immediately alongside individual bowls of strained au jus for dipping.