Pat the chuck roast dry and season generously with salt and pepper. Heat olive oil in a large skillet over medium-high heat. Sear the roast for 3-4 minutes per side, until a deep brown crust forms. Transfer the roast to the slow cooker.

In the same skillet, add the sliced onions and cook for 5-7 minutes, until they begin to soften. Add the minced garlic and cook for another minute until fragrant.

Pour in about 1/2 cup of the beef broth to deglaze the skillet, scraping up any browned bits from the bottom. Pour the onion mixture into the slow cooker. Add the remaining beef broth, Worcestershire sauce, soy sauce, and fresh thyme sprigs.

Cover and cook on low for 8-10 hours or on high for 4-5 hours. The beef should be very tender and easy to shred.

Carefully remove the beef from the slow cooker and place it on a cutting board. Shred the meat using two forks, discarding any large pieces of fat. Strain the cooking liquid (au jus) through a fine-mesh sieve into a bowl to remove the solids.

Preheat your broiler. Split the hoagie rolls and place them on a baking sheet. Toast them lightly under the broiler. Pile the shredded beef onto the bottom half of each roll, top with a slice of provolone cheese, and broil for 1-2 minutes until the cheese is melted and bubbly. Serve immediately with a side of warm au jus for dipping.