The rest of the garlic we chop coarsely. In our 13 × 9 inch glass baking pan, we put half a teaspoon of olive oil. We add the cut up potatoes, onions, carrots, celery, and garlic. We sprinkle this with salt and pepper and some rosemary.
We are now ready for the chicken. We cover our cutting board with wax paper. We rinse the chicken with cold water, dry with paper towels, and place on the wax paper. We want to remove the backbone and flatten the chicken. We do this by cutting along both sides of the backbone, which removes the backbone from the rest of the chicken. We save the backbone for stock along with the neck and the rinsed contents of the bag of innards (minus the liver, which we discard). After the chicken has been butterflied, we remove some of the excess fat (saving it for the stock as well).
We loosen the skin of the chicken from the breasts and thighs and put the sage mixture under the skin. We place the flattened chicken on top of the vegetables in the baking dish, skin-side up. We rub the rest of the olive oil on top of the chicken and sprinkle on some salt and pepper.
We place the chicken in the oven and cook for about 30 minutes. We baste the chicken every 10 minutes from this point on, until the chicken is browned and done. We want the leg-thigh joint to be 180 degrees. This takes us about 50 minutes in the oven.
We remove the chicken to a platter to rest for 10 minutes. Meanwhile, we turn the potatoes and vegetables over in the pan and return them to the oven to brown.
We serve the chicken with the potatoes and vegetables.