Prepare the ingredients: Chop the onion, garlic, and bell pepper. Cut the fish into 1-inch pieces. Peel and devein the shrimp if necessary. Scrub the mussels and clams.
Sauté the Aromatics: In a large stockpot or Dutch oven, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes until translucent. Add the garlic and bell pepper, cooking for another 3-4 minutes until they begin to soften.
Add the Herbs and Spices: Stir in the dried oregano, dried basil, crushed red pepper flakes (if using), and bay leaf. Cook for another minute to release their aromas.
Make the Broth: Add the crushed tomatoes, clam juice, white wine, chicken broth, salt, and black pepper. Stir well to combine and bring the mixture to a simmer. Let it cook for about 20 minutes, allowing the flavors to meld together.
Cook the Seafood: Add the fish pieces to the pot and cook for about 5 minutes. Then, add the shrimp, mussels, clams, and scallops. Cover the pot and cook for another 5-7 minutes until the mussels and clams have opened and the shrimp and scallops are cooked through. Discard any mussels or clams that do not open.
Finish the Dish: Stir in the fresh parsley and basil. Taste and adjust the seasoning with more salt and pepper if needed.
Serve: Ladle the cioppino into bowls and serve with crusty bread on the side to soak up the delicious broth.