Preheat oven to 350°F and line a 9×13-inch pan with parchment paper or spray with non-stick cooking spray.
In a large bowl with an electric hand mixer, beat together the cake mix, water, vegetable oil, and eggs or egg whites on medium-high speed for 2 minutes, scraping the bottom of the bowl as needed.
Use a rubber spatula to gently fold in the freeze-dried strawberries into the batter.
Pour batter into the prepared pan and use an offset spatula or spoon to spread the batter into an even layer.
Bake in preheated oven for 30-35 minutes, or until the top of the cake springs back when lightly touched.
Allow cake to cool for 20 minutes. Using a smoothie straw or the handle of a wooden spoon, poke holes across the cake, spaced every inch or so, halfway into the cake.
In a large liquid measuring cup with a spout, whisk together the strawberry jello mix and boiling water until the gelatin is fully dissolved. Carefully pour strawberry gelatin evenly over top of cake.
Cool completely on a wire rack.
Evenly spread the whipped topping onto the cake. Cover and refrigerate for at least 4 hours.
Just before serving, top with sliced strawberries.
