Preheat the oven to 350°F. Lightly grease a 9×13-inch baking pan.
Stir the strawberry gelatin into 2 cups boiling water until completely dissolved. Set aside to cool to room temperature. Do not add extra cold water.
Combine the crushed pretzels, melted butter, and 3 tablespoons sugar. Press evenly into the prepared pan. Bake for 10 minutes, then let the crust cool completely.
Beat the softened cream cheese and 1 cup sugar until smooth. Gently fold in the thawed whipped topping until evenly combined.
Spread the filling over the completely cooled crust, reaching every side and corner to seal the crust underneath. Refrigerate for 30 minutes.
When the gelatin has cooled to room temperature, stir in the sliced strawberries. Refrigerate, checking frequently, until slightly thickened but still able to flow off a spoon. Do not let it set completely in the bowl.
Gently spoon the strawberry mixture over the chilled cream cheese layer and distribute evenly.
Refrigerate for at least 4 hours, and until the topping is fully set across the center. You can refrigerate overnight. Keep refrigerated until serving.