1. In a large bowl, combine crab meat, fennel fronds, serrano chile, 3 tablespoons olive oil, and salt; set aside.

2. Drizzle bread with remaining 1/4 cup olive oil. Heat a large nonstick skillet over medium heat. Add bread and cook, turning once, until golden and crisp on each side.

3. Remove bread from skillet and spread one side of each slice with aioli; top with crab mixture. Cut each slice of bread into quarters and top crab with a dollop of aioli. Serve immediately with lemon wedges.