01 - Preheat the oven to 325°F.
02 - Pat the beef chuck roast dry with paper towels and rub evenly with olive oil. Combine the kosher salt, black pepper, dried oregano, dried basil, garlic powder, and crushed red pepper flakes in a small bowl. Coat the roast thoroughly on all sides with the spice mixture.
03 - Heat a large Dutch oven or heavy oven-safe pot over medium-high heat. Sear the seasoned roast on all sides until deeply browned, approximately 2 to 3 minutes per side. Remove the roast and set aside on a plate.
04 - In the same Dutch oven, add the sliced onion and minced garlic. Sauté for 2 to 3 minutes until softened and fragrant, scraping up any browned bits from the bottom of the pot.
05 - Pour in the beef broth, water, and Worcestershire sauce. Add the Italian seasoning, sliced green bell pepper, and fennel seeds. Stir to combine, ensuring all the caramelized bits are lifted from the pot.
06 - Return the seared roast to the Dutch oven, nestling it into the liquid. Cover tightly with a lid and transfer to the preheated oven. Braise for 2.5 to 3 hours, or until the beef is fork-tender and easily shreds apart.
07 - Remove the roast from the pot and let it rest for 15 minutes. Strain the cooking liquid through a fine-mesh strainer into a bowl, discarding the solids. Skim off any excess fat from the surface of the au jus.
08 - Thinly slice the rested beef against the grain using a sharp knife or meat slicer for ultra-thin cuts. Return the sliced beef to the strained au jus and simmer over low heat for 5 to 10 minutes, allowing the meat to absorb the juices.
09 - Split the Italian rolls open and pile the juicy sliced beef generously onto each roll. Ladle extra au jus over the top. Finish with a generous spoonful of giardiniera and roasted sweet peppers to taste. Serve immediately with additional au jus on the side for dipping.