Cut your fruit into even sized pieces. If you only have a small amount of fruit, add tinned or frozen fruit so that you have 1 kilogram of fruit in total.
Pulse flour, oats, sugar, nuts, and salt in a food processor until nuts are chopped. Add butter and pulse until mixture begins to clump. If you don’t have a food processor, mix the flour, oats, sugar and salt together. Chop the nuts and add to the bowl. Add the butter and use your hands to rub all of the ingredients together until they are crumbly. Mix through any optional toppings.
Grease a 24cm (or similar) oven proof dish. Spread fruit evenly on the bottom and sprinkle the crumble on top.
Bake crumble in the middle of oven until fruit is tender and topping is golden brown, about 25 to 30 minutes.