Preheat the oven to 375°F. Lightly grease a 9×13-inch baking dish.
Make the pretzel crust. Combine the crushed pretzels, melted butter, and 3 tablespoons sugar in a bowl. Stir until the pretzels are evenly coated.
Press the pretzel mixture firmly and evenly into the bottom of the prepared baking dish.
Bake for 10 minutes. Remove from the oven and let the crust cool completely.
Make the creamy filling. Beat the softened cream cheese and ¾ cup sugar with an electric mixer until smooth and fluffy.
Gently fold in the thawed Cool Whip until fully combined.
Spread the cream cheese mixture evenly over the completely cooled pretzel crust. Refrigerate for at least 1 hour.
Prepare the strawberry gelatin. Add the strawberry Jell-O to a large bowl. Pour in the boiling water and whisk until the gelatin is completely dissolved.
Let the gelatin mixture cool to room temperature. Do not pour it over the cream cheese layer while it is still warm.
Arrange the sliced strawberries evenly over the chilled cream cheese layer.
Slowly pour the cooled gelatin mixture over the strawberries, covering them evenly.
Refrigerate for at least 4–6 hours, or overnight, until the gelatin is completely firm.
Slice into 9 servings and serve chilled.