Brown the Sausage: Heat 1 tablespoon of olive oil in a skillet over medium-high heat. Brown the hot Italian sausage for about 5 minutes, ensuring it's cooked through, then transfer it to your slow cooker.

Sauté Onions and Garlic: In the same skillet, add chopped onions and cook until they're softened and lightly browned, around 8-10 minutes. Stir in the minced garlic for 30 seconds until fragrant.

Deglaze and Transfer: Add the tomato paste, dried oregano, crushed red pepper flakes, dry red wine, and beef broth into the skillet. Bring this mixture to a boil, scraping up any delicious bits from the bottom, then pour it into the slow cooker.

Combine Remaining Ingredients: Add crushed tomatoes, tomato sauce, diced tomatoes, Calabrian hot pepper paste, and bell peppers into the slow cooker. Mix everything well.

Cook: Cover and let the ragu cook on LOW for 8-10 hours or HIGH for 6-7 hours.

Finish and Adjust Flavor: Once cooked, stir in the chopped parsley and season with salt and pepper to taste. Optionally, add a splash of wine for extra flavor.