Preheat oven to 450 degrees and set the rack in the center.
Place fennel seeds in a small frying pan and toast over medium heat until fragrant. Place seeds in a small bowl and combine with olives, juice, zest, and 1 tablespoon of the olive oil. Season with salt and freshly ground black pepper and set aside to marinate, at least 15 minutes.
Heat a large ovenproof 12-inch frying pan over medium heat. Rub chicken with remaining 1 tablespoon of olive oil and season with salt and pepper. Add chicken to the pan, skin side down, and cook until golden brown, about 3 minutes. Flip chicken over with tongs and put it in the oven to finish cooking. (If you're not using an ovenproof frying pan, transfer the chicken to a baking dish first). Roast chicken for about 15 minutes, or until the internal temperature registers 160 to 165 degrees on a meat thermometer.
Take the chicken out and let it rest for 5 minutes so that the juices settle. Transfer to a serving plate and top with reserved olive mixture. Serve.