Preheat oven to 350°F (175°C).
Add sliced apples to a bowl.
Add lemon juice, sugar, flour, cinnamon, and nutmeg.
Toss well to coat the apples.
Pour the apple mix into a baking dish.
In another bowl, combine oats, brown sugar, flour, cinnamon, and salt.
Add cold butter cubes.
Mix with fingers until crumbly.
Spread crumble topping over apples evenly.
Bake for 40 minutes until golden and bubbly.
Cool slightly before serving.