Preheat the oven to 400ºF.
To make the filling, stir together the apples, blackberries, apple juice, and sugar in a large bowl. Place fruit into an 8-by-8-inch baking dish.
To make the crumble, place the butter, sugar, flour, and almonds in a food processor and pulse until the mixture resembles bread crumbs. Mix in the hazelnuts and oats.
Sprinkle the crumble over the filling and bake in the oven for 20 to 25 minutes, or until the fruit is bubbling and the crumble is toasted.