Preheat your oven to 350°F (175°C).
Grease and flour a 9x13 inch baking pan.
Prepare the vanilla cake mix according to package instructions.
Pour the batter into the prepared pan and bake for 30 minutes.
Allow the cake to cool for about 10 minutes.
Poke holes in the cake using a fork, spaced about 1 inch apart.
Mix the strawberry gelatin with 1 cup of boiling water until dissolved.
Pour the gelatin mixture over the poked cake.
Refrigerate the cake for at least 2 hours to set.
Spread the whipped topping mixture over the chilled cake.
Decorate with sliced strawberries.