Peel and slice all your apples thin. Place them into the large bowl. Toss them with lemon juice and sugar.

Sprinkle cinnamon over the sliced apples. Stir them until they are well coated. Pour the apples into the baking dish.

Mix flour and brown sugar in a bowl. Add the oats and a pinch salt. Stir these dry ingredients together well.

Add the cold butter to the flour. Use your pastry cutter or a fork. Work it until it looks like crumbs.

Sprinkle the topping over the apples evenly. Do not press the topping down hard. It should stay light and crumbly.

Place the dish into the hot oven. Bake for about forty-five minutes. The top should be dark golden brown.

Remove the dish from the oven carefully. Let it sit for ten minutes. This helps the juices thicken up.