01 - Arrange the thinly sliced onion and minced garlic evenly across the bottom of the slow cooker insert.
02 - Combine the kosher salt, black pepper, Italian seasoning, dried basil, and oregano. Rub the seasoning mixture over all sides of the chuck roast, pressing gently to adhere.
03 - Place the seasoned chuck roast on top of the onion and garlic bed in the slow cooker.
04 - Pour the beef broth and pepperoncini juice over the roast. Sprinkle with crushed red pepper flakes if additional heat is desired.
05 - Secure the lid and cook on LOW for 8 hours or on HIGH for 5 to 6 hours, until the beef is fork-tender and shreds apart effortlessly.
06 - Transfer the roast to a large cutting board. Using two forks, shred the meat, discarding any large pieces of excess fat. Return the shredded beef to the slow cooker and toss to coat in the accumulated juices.
07 - If desired, spread softened butter on the cut sides of each roll and toast under the broiler until golden brown, about 1 to 2 minutes.
08 - Mound the shredded beef generously onto each toasted roll. Layer with provolone cheese slices and jarred pepperoncini.
09 - For a finishing touch, place the assembled sandwiches under the broiler for 1 to 2 minutes until the cheese is melted and bubbly. Serve immediately while warm.