Preheat oven to 350 degrees F (175 degrees C). Prepare a 9×13-inch baking dish with cooking spray.
Mix flour, brown sugar, oats, coconut, and walnuts together in a bowl. Pour melted butter over the flour mixture and mix. The mixture should clump together easily when compressed.
Press about half the flour mixture into the bottom of the prepared baking dish; top with a layer of raspberry preserves. Finish by topping with the remaining flour mixture, patting lightly to complete the ‘crust.’
Bake in preheated oven until browned, 20 to 25 minutes. Cool completely before cutting to serve.