Gently use your fingers to pull the skin away from the breasts and down to the thighs.
Be careful not to tear the skin.
Make a paste of finely minced garlic, rosemary, sage, and olive oil.
Spread the paste under the skin.
Fill a coffee filter (or cheesecloth) with 3 cloves garlic, 2 tbsp. rosemary, 2 tbsp. sage, and 2 tbsp. thyme, and 2 quarters of the onion.
Place mixture in the cavity.
Tie off the legs, place in the roaster and brush the bird with additional olive oil.
Tuck in the wing tips so they don’t burn.
Place remaining half of the onion in bottom of the pan.
Roast for 15 minutes at 450° degrees, lower the heat to 375°.
Cover, roast for an hour or so before removing lid.
Baste and continue roasting until internal temperature is at least 165-170°.
Baste with more olive oil once or twice during cooking time.
Remove and discard the coffee filter or cheesecloth with spices and the onions from bottom of the pan.
Slice and serve.