Preheat oven to 375 degrees F (190 degrees C).
Combine strawberries, 3 tablespoons white flour, sugar, and vanilla extract in a large bowl and mix thoroughly. Pour into a 9×13-inch baking dish.
Combine 1 1/2 cup flour, 1 1/4 cup sugar, butter, rolled oats, and salt in a bowl; mix by hand or with a pastry cutter until crumbly and well mixed. Spread over strawberry mixture.
Bake in the preheated oven until bubbly and light brown, about 45 minutes.