To prepare garlic dip, spoon yogurt onto several layers of heavy-duty paper towels; spread to 1/2-inch thickness. Cover with additional paper towels; let stand 5 minutes. Scrape into a bowl using a rubber spatula. Place salt and garlic in a mortar; crush with a pestle until smooth. Drizzle with 1 tablespoon oil; stir with a small whisk. Add garlic mixture and 1 tablespoon juice to yogurt. Cover and chill.
To prepare the chicken, remove and discard the giblets and neck from the chicken. Rinse chicken with cold water, and pat dry. Trim excess fat. Starting at the neck cavity, loosen the skin from breast and drumsticks by inserting your fingers, gently pushing between the skin and meat. Combine 2 tablespoons juice and remaining ingredients. Rub juice mixture under loosened skin and inside body cavity. Place chicken in a large zip-top plastic bag; seal and marinate in refrigerator 1 hour.
Preheat oven to 350°.
Remove chicken from bag; place chicken, breast side up, on a broiler pan. Insert meat thermometer into meaty part of thigh, making sure not to touch bone. Bake at 350° for 1 hour and 10 minutes or until thermometer registers 180°. Cover chicken loosely with foil, and let stand for 10 minutes. Discard skin. Serve with garlic dip.