Preheat your oven to 350°F (175°C) to ensure even baking.

In a large mixing bowl, combine sliced peaches, lemon juice, vanilla extract, arrowroot, salt, and sugar to taste. Stir gently and let sit to absorb flavors.

Spread the peach mixture evenly in a buttered 2.5-quart baking dish.

In a separate bowl, whisk together flour, brown sugar, and ground cinnamon. Cut in cold butter until the mixture resembles coarse crumbs.

Stir in rolled oats until well blended with the crumble mixture.

Sprinkle the crumble topping evenly over the peach filling in the baking dish.

Bake for 40 minutes until the topping is golden brown and edges bubbly.

Remove from oven and let cool for about 10 minutes before serving.