Preheat the oven to 450 degrees F. Remove any giblets or innards from the chicken and rinse the chicken under cool water. Pat it dry both inside the cavity and over the skin, then trim away any excess or floppy skin and fat and gently cut out the wishbone with a paring knife (this is located beneath the "V" at the top of the chicken breast).
Combine the olive oil, onion powder, salt, pepper and garlic in a small bowl and stir together with a fork to form a paste.
Tuck the chicken's wing tips underneath the back of the breasts. Starting at the top of the breast, slide your fingers underneath the chicken skin, working to loosen the skin from the meat all over the bird, including around the legs and thighs. (Work slowly, and take extra care not to tear the skin.)
Reserve 1 tablespoon of the spice rub, then rub the rest of the spice mix underneath the loosened skin all over the meat. (Be sure to try to reach the leg and thigh meat!) Rub the reserved tablespoon of spice mix all over the top of the chicken skin. Cross the chicken legs and tie them together at the bone with butcher's string.
Scrunch a 12-inch piece of heavy-duty aluminum foil together and shape into a ring about 3 inches in diameter. Place the foil ring in the center of a roasting pan and set the chicken on top of it, breast-side up.
Place the pan in the center of the oven and roast 35 minutes. Remove the whole pan from the oven and use a pair of strong tongs to flip the entire chicken over so that it now rests on the foil ring breast-side down (wing tips up). Return the pan to the oven and roast until a meat thermometer inserted into the thickest part between the leg and thigh reads 165 degrees F, 10 to 15 minutes longer.
Remove the pan from the oven, flip the chicken back to breast-side up and tent a piece of aluminum foil over the top of the chicken. Allow the chicken to rest for at least 15 minutes before carving.