Start by patting the beef chuck roast dry with paper towels and seasoning it generously with salt and pepper.
In a large skillet over medium-high heat, add the olive oil. Once hot, sear the beef on all sides until it’s browned (about 3-4 minutes per side). Remove from heat.
In the bottom of the slow cooker, combine the sliced bell pepper, onion, and minced garlic.
Place the seared beef roast on top of the vegetables in the slow cooker.
Pour in the beef broth and the diced tomatoes, followed by the Italian seasoning and red pepper flakes.
Cover and cook on low for 8 hours or on high for 4 hours, until the beef is tender and easily shredded with a fork.
Once cooked, remove the beef from the slow cooker and shred it using two forks. Return the shredded beef to the pot, mixing it well with the sauce and vegetables.
Serve the Italian beef on hoagie rolls, garnishing with fresh basil leaves for an extra burst of flavor.