Place onion rings in a large roasting pan or baking dish. Add 4 garlic cloves, 2 sprigs each of rosemary and thyme and 2 sage leaves. Drizzle with 2 tablespoons olive oil, 1/2 teaspoon salt and pepper. Stir to coat well. Make a space in the middle to make room for the chicken.
Remove giblets, neck and tail fat from the chicken. Rinse chicken under cold, running water. Drain and pat dry with paper towel. Place 4 garlic cloves, 2 sprigs, each of rosemary and thyme and 2 sage leaves inside the cavity of the chicken. Place it in the center of the onions, breast side up, and drizzle with remaining 2 tablespoons olive oil. Season chicken with remaining salt and more pepper. Place pan in the middle of the oven and roast for 30 minutes.
Reduce heat to 375°F and continue cooking for 50 to 75 minutes until an instant-read thermometer inserted into the thigh registers 180° F.
Tent with aluminum foil. Let rest for 15 minutes to allow the juices to distribute evenly throughout. Transfer chicken to a serving platter. Using a slotted spoon, transfer the cooked onions to the same platter.
Note: Pour the pan juices into a fat separator or degreasing cup so the fat floats to the top. Pour juices (without the fat) into a small saucepan and simmer over medium heat for 2 to 3 minutes until reduced by half. Pour this concentrated sauce over the chicken just before serving.
HELPING HANDS: Kids can help season and stir the onions.