Pat the chuck roast dry with paper towels and season all over with salt and pepper. Heat olive oil in a large skillet over medium-high heat. Carefully place the roast in the skillet and sear for 4-5 minutes per side, until a deep brown crust forms.

Transfer the seared roast to the basin of a large slow cooker. Add the sliced onion, minced garlic, beef broth, and Worcestershire sauce. Cover and cook on LOW for 8 hours or on HIGH for 4 hours, until the beef is tender and shreds easily with a fork.

Carefully remove the beef from the slow cooker and place it on a large cutting board. Use two forks to shred the meat. Strain the liquid from the slow cooker through a fine-mesh sieve into a bowl or saucepan; this is your au jus. Discard the solids.

Preheat your broiler. Open the hoagie rolls and place them on a baking sheet. Toast them lightly under the broiler for 1-2 minutes. Pile the shredded beef onto the bottom half of each roll, top with a slice of provolone cheese, and broil for another 1-2 minutes until the cheese is melted and bubbly. Place the top of the roll on and serve immediately.

Serve the sandwiches hot with small bowls of the warm au jus for dipping.