Pat the chuck roast dry. Season it generously on all sides with salt and pepper.

Place the roast in the slow cooker. Spread the sliced onion and minced garlic on and around the meat.

Whisk the beef broth, Worcestershire sauce, and dried thyme in a bowl. Pour the mixture over the roast and onions.

Cover and cook on low for 8 hours, or until the meat is fork-tender and pulls apart easily.

Transfer the roast to a cutting board and shred with two forks. Discard any large pieces of fat.

Pile the shredded beef onto hoagie rolls. Top with provolone if using, then place under a hot broiler or in a hot oven just long enough to melt the cheese and lightly toast the roll.

Strain the cooking liquid through a fine-mesh sieve into a bowl. Skim off excess fat and serve the warm strained liquid as au jus for dipping.