Marinate chicken: Mince and mash garlic to a paste with ½ teaspoon salt, then transfer to a large bowl. Stir in olive oil, lime juice and cumin. Toss chicken within marinade until coated. Cover, put in the fridge and marinate for at least 1 hour.
Position a rack in the center of the oven and heat at 425°F.
Place the chicken on a baking sheet and roast for about 15 minutes. Take the baking sheet out the oven and place the lime slices on top of the chicken evenly.
Continue roasting until the chicken is cooked through, about 40 minutes more and serve.