In the bottom of a slow cooker, add the onion, garlic, tomato paste, banana peppers and the juices from the jar, 1/4 cup broth, and Italian seasoning and stir until well combined. Set aside.
Pat dry the chuck roast and season on both sides with salt and pepper, pressing the seasonings into the meat. Sprinkle and rub the flour so that it evenly coats both sides of the roast.
Heat the oil in a large skillet over medium-high heat. Add the roast and brown on both sides until a golden-brown crust forms. (I know it’s annoying to brown the meat before the slow cooker, but I think it really adds flavor to the meat, plus the flour that coats the beef helps thicken the sauce a bit).
Nestle the meat into the slow cooker, cover and cook on high for 6 hours, or low for 8 to 10 hours, or until the meat is cooked through and fall apart tender.
Transfer the meat to a baking sheet and shred using two forks. Transfer back to the slow cooker and toss to coat in the liquid, cover and keep on ‘warm’ until ready to build your sliders. The longer it sits in the liquid on warm, the more flavorful and tender the meat!