Season the chuck roast with Kosher salt and black pepper.
Heat the olive oil in a large skillet or Dutch oven over medium-high heat. When the pan is hot, place the meat in the pan and sear on all sides until golden brown, a few minutes per side. Transfer the meat to a slow cooker.
In a small bowl, combine the basil, oregano, parsley, thyme, onion powder, and red pepper flakes. Sprinkle the mixture over the beef.
Add the beef broth, sliced pepperoncini, pepperoncini liquid, onion, bell pepper, and garlic. Give the mixture a little stir.
Put the lid on the slow cooker and cook on LOW for 8 hours or on HIGH for 3 to 4 hours, or until meat is cooked and tender.
Remove the beef and shred with a fork. Place the shredded beef back into the slow cooker with the juices, onion, peppers, and pepperoncini.
Preheat the broiler. Split the buns or rolls in half and butter the insides. Place the buns or rolls butter side up on a baking sheet. Place under the broiler until lightly toasted. Don’t walk away, they will toast quickly.
Use a slotted spoon to drain off some of the liquid so the sandwich doesn't get soggy. Place the shredded meat mixture on top of the toasted buns or rolls. Add provolone cheese slices. The cheese should melt because the beef will be hot. If you want, you can place the sandwiches under the broiler for a few seconds to quickly melt the cheese. Top the sandwiches with giardiniera, if desired. Serve immediately.
