Preheat your oven to 350° F. Butter a 9x13" pan and set it aside.
Place your oats, cassava flour, tapioca flour, maple syrup, baking soda, salt, cinnamon, and coconut sugar in a food processor. Pulse until combined.
Cut up the cold butter into tablespoon size pieces. Place the butter pieces in the food processor and pulse until the mixture turns into a crumble.
Spoon out enough crumble mixture to cover the bottom of the 9x13" pan (about 1/2 of the crumble mixture). Pat the crumble mixture into a crust in the 9x13" pan. Set the rest of the crumble mixture aside.
Place the peaches and coconut sugar for the filling mixture into a large saucepan. Bring to a simmer over medium heat. Once the peach mixture is simmering, turn the heat down to low and simmer for 8 minutes. Mash the peaches while they are simmering.
After the peach mixture has simmered for 8 minutes, add the tapioca flour. Stir in the flour and simmer for 1-2 more minutes, stirring constantly.
Pour the peach filling onto the crust in the 9x13" pan. Spread the remaining crumble evenly over the peach filling.
Bake for 35-40 minutes. Cool completely before cutting and serving. Store these bars in an airtight container in the refrigerator.