Prepare the fruit mixture by peeling, coring, and slicing the apples, and hulling and halving the strawberries. Combine in a bowl with lemon juice, 1/4 cup sugar, and cinnamon.
Make the crumble topping by mixing oats, almond flour, melted butter, remaining sugar, and salt in a separate bowl until crumbly.
Assemble the crumble by pouring the fruit mixture into a greased 9-inch baking dish and topping it with the crumble mixture.
Bake in a preheated oven at 350°F for 30-35 minutes until bubbly and golden brown. Let cool for 10 minutes before serving.