Preheat your oven to 375°F (190°C). Lightly grease an 8x8 or 9x9 inch baking dish.
In a large bowl, combine the peeled and sliced peaches with 1 tablespoon of the granulated sugar. Toss gently to coat and set aside.
In a separate medium bowl, combine gluten-free oats, sliced almonds, gluten-free baking flour, brown sugar, remaining 2 tablespoons granulated sugar, kosher salt, and cut butter pieces. Use your fingertips or a pastry blender to cut the butter into the dry ingredients until the mixture resembles coarse crumbs.
Stir in the vanilla extract and water until just combined.
Pour the sugared peaches into the prepared baking dish, spreading them evenly.
Crumble the oat and almond topping mixture evenly over the peaches.
Bake for 30-35 minutes, or until the topping is golden brown and the peaches are bubbling and tender when pierced with a fork.