Preheat oven to 375°. Mix filling ingredients in a bowl, making sure that the corn starch is evenly distributed and dissolved. Empty into a 9” round pie dish.
Mix dry ingredients of crumble in a large bowl with a whisk. Add in oil and mix until topping forms a sandy-textured crumble that holds together relatively well. Sprinkle evenly over top of fruit filling.
Place a piece of tin foil or a cookie sheet on the rack below the crumble to catch strawberry juice spillage. Check on it around 45 minutes, but total bake time should be about 1 hour and 10 minutes, or until the filling is oozing and bubbly and the crumble is nicely browned on top. Let cool at least 20 minutes. Enjoy with whipped cream (make your own, with a drizzle of vanilla and maple syrup—you’ll never go back!).