To make a JELL-O cake, pour a mixture of 1 cup boiling water, a 3-ounce package of JELL-O and 1/2 cup cold water over a slightly cooled cake pierced with a fork. Cool the cake for three hours in the refrigerator. Top the cake with thawed whipped topping.
A classic flavor combination for JELL-O cake is a white cake with strawberry JELL-O, but trying different flavor combinations changes the recipe. Try a lemon cake with lime JELL-O, or use any flavor of JELL-O with a white cake. Prepare the cake according to the recipe or box instructions. Bake the cake in a 9-by-13-inch baking pan.
Let the cake cool for about 15 minutes. Use a fork to poke holes all over the cake top with 1/2-inch spaces. Dissolve the gelatin mix completely in the boiling water. Stir it for about two minutes so the powder fully dissolves. Add the cold water to the mixture, and stir it again to incorporate it completely.
Pour the mixture gently over the cake. Move the liquid around the cake as you pour so it covers the top evenly. After the cake chills for at least three hours, spread an even layer of whipped topping on the top before serving. Garnish the top of the cake with strawberry slices if desired.