01 - Preheat oven to 325°F (163°C).
02 - Pat the beef chuck roast dry with paper towels. Rub evenly with olive oil. In a small bowl, combine kosher salt, black pepper, dried oregano, dried basil, garlic powder, and crushed red pepper flakes. 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, approximately 2 to 3 minutes per side, until a deep golden-brown crust forms.
04 - Remove the roast and set aside. In the same pot, 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, Worcestershire sauce, Italian seasoning, sliced green bell pepper, and fennel seeds. Stir well, bringing the liquid to a gentle simmer while deglazing the pot to release all flavorful fond.
06 - Return the seared roast to the pot, ensuring it is partially submerged in 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 pulls apart.
07 - Remove the roast from the pot and let rest for 15 minutes on a cutting board. 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. For ultra-thin shavings, use a meat slicer or electric knife. Return the sliced beef to the strained au jus and simmer gently for 5 to 10 minutes, allowing the meat to absorb the flavorful broth.
09 - Split the Italian rolls or hoagie buns lengthwise. Pile the hot, jus-soaked beef generously onto each roll. Ladle extra au jus over the top. Finish with a heaping spoonful of giardiniera and roasted sweet peppers to taste.
10 - Serve immediately alongside small bowls of extra au jus for dipping. For a wet-style sandwich, briefly dip the split roll in the au jus before adding the beef.