01 - Arrange the thinly sliced onion and minced garlic evenly across the bottom of the slow cooker.
02 - Rub the chuck roast on all sides with kosher salt, black pepper, dried Italian seasoning, basil, and oregano until evenly coated.
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 crushed red pepper flakes over the top if additional heat is desired.
05 - Cover the slow cooker 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 - Remove the roast from the slow cooker and shred the meat using two forks, discarding any excess fat. Return the shredded beef to the juices in the slow cooker and stir to combine.
07 - If desired, spread softened butter on the cut sides of the sandwich rolls and toast under the broiler until golden brown.
08 - Pile the shredded beef generously onto each roll. Top with provolone cheese slices and jarred sliced pepperoncini.
09 - Place the assembled sandwiches under the broiler for 1 to 2 minutes until the cheese is melted and bubbly. Serve warm.