Crispy Rosemary Roast Chicken

Dry chicken thoroughly with paper towels. Using a sharp knife, cut a slit through the back of the chicken to allow juices to escape during roasting. Turn chicken over, and using fingers, separate the skin from the breast, thighs, and legs trying not to tear skin. Lift skin and sprinkle garlic salt and pepper liberally all under skin, then all over skin on all sides. Place on a rack (putting something under rack to catch juices) in fridge overnight and do not cover. Next day. Rub chicken all over with olive oil, place rosemary sprigs under skin. Preheat baking pan with rack in 450F oven. When heated, place chicken breast side down on rack and roast for 30 minutes. Using paper towel wads, turn chicken breast side up and roast another 30 minutes or until instant thermometer registers 165F. Remove from oven and slit skin between leg and breast to pour out chicken juices into pan. Remove chicken to a wire rack to rest for 10 minutes before carving. Meanwhile heat juice in pan to boiling and adjust seasoning before serving as pan sauce with carved chicken.