In a large freezer safe dish, mix lemon juice sugar and water. Stir until sugar has completely dissolved. Add in 12 ice cubes. Carefully transfer to the freezer. Every hour, for 4 to 6 hours, take a fork and break up the lemonade. When desired consistency is reached, transfer to glasses. Store remaining in in the freezer. Thaw slightly in the refrigerator or on the counter until easily crushable.