Preheat oven to 350°F.
Add 5 cups chopped apples, ½ cup light brown sugar, 2 tablespoons all-purpose flour, 1 tablespoon lemon juice, 1 teaspoon vanilla extract, 1 teaspoon ground cinnamon, ¼ teaspoon ground nutmeg, and ¼ teaspoon salt to a large bowl and stir until evenly coated. Transfer the mixture to a 9x9-inch baking dish.
Place the slices of ½ cup cold butter on top of the apple mixture.
Mix together the 1 cup 1-minute oats, 1 cup light brown sugar, 1 cup all-purpose flour, ½ teaspoon ground cinnamon, and ½ cup cold butter until a crumble forms. You can use a pastry cutter or I prefer to work with my hands. Spread the topping out over the apple mixture.
Bake for 35 to 40 minutes until the crisp is browning and the apple mixture is bubbling around the edges.
Remove from oven and serve warm or at room temperature with ice cream and whip cream.