1. **Prep the Ingredients:**
- Dice the onion, mince the garlic, thinly slice the fennel bulb, and dice the bell pepper on the cutting board using the knife.
- Cut the fish into chunks, and clean the shellfish.
2. **Sauté the Aromatics:**
- Heat the skillet over medium heat and add the olive oil.
- Sauté the diced onion, garlic, fennel, and bell pepper with a wooden spoon or spatula until softened, about 5-7 minutes.
3. **Combine in the Slow Cooker:**
- Transfer the sautéed vegetables to the slow cooker.
- Add the diced tomatoes (with their juice), seafood or fish stock, white wine, saffron threads, smoked paprika, thyme, basil, bay leaf, salt, and pepper.
- Stir to combine using the wooden spoon or spatula.
4. **Cook:**
- Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the flavors have melded together.
5. **Add the Seafood:**
- About 30 minutes before serving, add the chunks of white fish, shellfish, and shrimp to the slow cooker.
- Cover and cook on high until the seafood is just cooked through and the shellfish have opened (discard any that do not open).
6. **Serve:**
- Use the ladle to transfer the bouillabaisse into bowls, making sure to get a good mix of seafood and broth.
- Garnish with chopped fresh parsley.
- Serve with lemon wedges on the side for squeezing over the top.