Stir boiling water into Jell-O. Mix in a large bowl at least 2 minutes until completely dissolved. Add enough ice to cold water to measure 1 cup. Add gelatin, stir until slightly thickened. Remove any unmelted ice. Add Cool Whip. Stir with wire whisk until well-blended. Stir in chopped strawberries. Refrigerate 20 to 30 minutes until very thick. Spoon into crust. Refrigerate 6 hours. Top with sliced strawberries.