Preheat the oven to 160ºC (fan) or 180ºC (conventional).
Wash and trim the strawberries, then peel and chop the apples. Place the fruit in a large mixing bowl.
Add the lemon juice, plain flour, and caster sugar to the fruit. Toss everything well to combine.
Transfer the fruit mixture to an oven-safe baking dish or a cast-iron skillet.
For the crumble topping, combine the butter, brown sugar, rolled oats, ground almonds, cinnamon, and plain flour in a separate bowl. Rub the butter into the dry ingredients using your fingertips until the mixture resembles coarse crumbs with pea-sized bits. Alternatively, pulse the ingredients in a food processor until the mixture resembles chunky breadcrumbs.
Sprinkle the crumble topping evenly over the fruit mixture.
Bake in the preheated oven for 25-30 minutes, or until the fruit is soft and bubbling around the edges, and the topping is golden brown.
Remove from the oven and let cool for about 5 minutes. Serve warm with scoops of vanilla ice cream.