01 - Preheat your oven to 425°F.
02 - In a small bowl, combine the minced garlic, lemon zest, lemon juice, olive oil, salt, pepper, thyme, and rosemary to make the marinade.
03 - Pat the chicken dry with paper towels. Gently loosen the skin over the breast and rub half of the marinade directly onto the meat under the skin. Rub the remaining marinade all over the outside of the chicken.
04 - Stuff the chicken cavity with the lemon slices and a few sprigs of extra thyme or rosemary, if desired.
05 - Arrange the onions, carrots, and celery in a large roasting pan. Place the chicken on top of the vegetables, breast side up.
06 - Roast for 1 hour 15 minutes, or until the juices run clear when the thigh is pierced, and a meat thermometer inserted into the thickest part of the thigh reads 165°F.
07 - Let the chicken rest for 10-15 minutes before carving. Serve with the roasted vegetables and pan juices.