Clam and Mussel Toasts

Name: Clam and Mussel Toasts
Ingredients: 1⁄2 cup extra-virgin olive oil, divided, plus more for drizzling; 4 oz. pancetta, finely chopped; 8 garlic cloves, 4 thinly sliced, 4 left whole; 1 medium sweet onion, finely chopped; 1 small fennel bulb, finely chopped, plus ½ cup fennel fronds; Four 3-inch-long strips of lemon zest; 1 bay leaf; 1 tsp. ground fennel seed; 2 cups dry white wine, divided; Four 1 ½-inch-thick slices sourdough bread, halved crosswise to make 8 pieces total; 1 lb. Manila clams, littleneck clams, or cockles, cleaned and purged; 1 lb. mussels, cleaned; 1⁄2 cup Italian parsley leaves and some tender stems; Red pepper flakes, for serving