Brothy Seafood Chowder

Name: Brothy Seafood Chowder
Ingredients: 3 Tbsp. extra-virgin olive oil; 2 lb. fish bones, rinsed; 1 small onion, unpeeled, quartered; 2 stalks celery, chopped; 1 leek, dark green parts chopped, rinsed, white parts cut into ¼ rounds, rinsed, reserved for stew; 1 dried chile de árbol or ½ tsp. crushed red pepper flakes; 1 garlic clove, smashed; 6 thyme sprigs; 2 bay leaves (optional); ½ cup dry white wine or sake; 1 Tbsp. fennel seeds; 1 lb. small Yukon Gold potatoes, quartered; Kosher salt; 1 fennel bulb, halved lengthwise, thinly sliced crosswise, fronds reserved for serving; 1½ lb. boneless, skinless white fish (such as cod), cut into 1 pieces; 2 cups Sun Gold tomatoes; Extra-virgin olive oil (for drizzling); Freshly ground black pepper