Preheat oven to 350 degrees F.
To a 9" pie plate (or other baking dish), add sliced peaches, fresh lemon juice, tapioca starch, cinnamon and vanilla. Mix until peaches are evenly coated.
7 peaches, cut into ½" slices , 1 tablespoon fresh lemon juice, 2 tablespoons tapioca starch , 1 teaspoon cinnamon , 1 teaspoon pure vanilla extract
Make the oat topping by adding the oat flour, oats, coconut sugar, walnuts, and salt to a medium sized mixing bowl. Mix until combined.
¾ cup oat flour, ¾ cup rolled oats/old-fashioned oats, ⅓ cup coconut sugar , ¾ cup chopped walnuts, ¼ teaspoon fine sea salt
Add the cubed butter to the oat mixture. Using a pastry cutter, cut the butter into the oat mixture (you can also use your hands to incorporate). You want the mixture to be coarse and crumbly, with little loose flour/oats.
½ cup cold butter, cut into cubes
Sprinkle the oat mixture over the peaches. Bake for 40-45 minutes, or until crumb topping is golden brown and edges are bubbly.
Let sit for 15 minutes before serving. This is very important as it further allows the arrowroot to thicken the fruit filling.
Serve and enjoy!