Stir boiling water into dry gelatin mix in large bowl at least 3 min. until gelatin is completely dissolved. Pour into 13x9-inch pan. Refrigerate at least 3 hours or until firm. Dip bottom of pan in warm water 15 sec. Cut into 24 decorative shapes, using 2-inch Halloween-shaped cookie cutters, making sure to cut all the way through gelatin to bottom of pan. Lift gelatin shapes from pan. Store in tightly covered container in refrigerator.