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. Mix thoroughly to create a uniform marinade.
03 - Pat the chicken completely dry with paper towels. Gently loosen the skin over the breast area and rub half of the marinade directly onto the meat beneath the skin. Rub the remaining marinade evenly over the entire exterior surface of the chicken.
04 - Place the lemon slices inside the chicken cavity along with additional fresh thyme or rosemary sprigs if desired.
05 - Distribute the quartered onions, carrot chunks, and celery pieces evenly across the bottom of a large roasting pan. Position the chicken on top of the vegetables, breast side facing up.
06 - Roast for 1 hour and 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 registers 165°F.
07 - Allow the chicken to rest for 10 to 15 minutes before carving. Serve accompanied by the roasted vegetables and pan juices.