Preheat oven to 400°. Line two rimmed baking sheets with foil and set a wire rack in each. Arrange bacon on racks in a single layer (some overlapping is okay).
Mix brown sugar, pepper, and fennel and sprinkle over bacon. Bake until bacon is crisp, 25 to 30 minutes, rotating pans halfway through.
Let bacon cool to warm room temperature so sugar will harden. Arrange the pieces in an airy heap in small bowls.