01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with cooking spray or butter. Prepare the cake mix according to package instructions, typically combining with eggs, oil, and water. Pour batter into the prepared dish and bake as directed on the box, usually 25-30 minutes, until a toothpick inserted in the center comes out clean. Let the cake cool for 20 minutes.
02 - Using the tines of a fork or the handle of a wooden spoon, poke holes evenly across the entire surface of the cooled cake. Press down firmly, reaching nearly to the bottom of the pan, to create channels for the gelatin to seep through.
03 - In a medium heat-safe bowl, empty the strawberry gelatin powder. Pour 1 cup of boiling water over the gelatin and stir continuously for 2 minutes until completely dissolved. Add 1/2 cup of cold water and stir to combine.
04 - Carefully pour the liquid gelatin mixture evenly over the surface of the cake, ensuring it distributes across the entire top. The gelatin will naturally seep into the poked holes, infusing the cake with strawberry flavor and creating a textured layer.
05 - Refrigerate the cake for at least 2 hours, or until the gelatin is completely set and firm to the touch. This step is essential for proper texture and makes the cake easier to cut and serve.
06 - Spread the whipped topping evenly over the entire surface of the chilled cake using an offset spatula or the back of a spoon. Arrange fresh sliced strawberries decoratively on top. For an elegant presentation, add fresh mint leaves as a garnish. Cut into squares and serve immediately, or keep refrigerated until serving.