Prepare a grill for medium-high heat or preheat broiler. If broiling, place chiles on a rimmed baking sheet. Grill, broil, or roast chiles directly over flame on stovetop, turning occasionally, until very tender and blackened all over, 10–12 minutes. Poblanos might take a little longer, so test doneness with a paring knife.
Transfer chiles to a large bowl. Cover with plastic wrap and let steam 15 minutes. Peel chiles. Halve lengthwise, discard seeds, and chop into 1/4" pieces.
Meanwhile, bring a medium pot of generously salted water to a boil. Cook shrimp until just opaque and pink, 2–3 minutes. Using a slotted spoon, transfer to an ice bath and let sit until cool, about 3 minutes. Drain and pat dry.
Mix chiles, tomato, jalapeños, Clamato juice, ketchup, olives, cilantro, onion, oregano, garlic, lime juice, oil, and 1/4 tsp. salt in a large bowl. Carefully fold in shrimp, crab, and avocado.
Transfer to a serving bowl or tall sundae glass and top with bay leaf, if using. Serve with tortilla chips alongside.
Salsa base (without seafood and avocado) can be made 1 day ahead. Transfer to a resealable container and chill.