Preheat the oven to 350 degrees F. Grease and lightly flour three 8-inch round cake pans. Set them aside. To make the cake, combine the cake mix, Jell-O, flour and sugar in a large bowl. Mix well. Add the oil. Add the eggs one at a time, beating well after each addition. Add the water and the half package of strawberries to this mixture. Mix well. Divide the batter evenly into the prepared pans.

Bake for 25-30 minutes or until a toothpick inserted into the middle of each layer comes out clean and the layers pull away from the sides of the pans. Transfer the layers from the oven to wire racks. Let them cool, still in their pans, for 10 minutes. After 10 minutes, run a knife around the inside edge of each pan, then unmold each layer onto the racks to cool completely.

To make the frosting, in a bowl, combine the remaining strawberries and the reserved juice with the confectioners' sugar and the butter. Beat with a mixer (or mash by hand) until smooth and well blended. Transfer the cake layers, one at a time, onto a serving platter. Frost between each layer, on top of the cake and around the sides with frosting.