Preheat oven to 350﮲F. Line an 8 inch square baking pan with parchment paper and spray with nonstick cooking spray. Set aside.
In a food processor or blender, process 11/2 cups of the oats into a fine flour. In a large bowl, combine (use a fork) the oat flour, remaining 1 cup oats, banana, flaxseed meal, water and salt until combined and crumbly.
In a large bowl, crush the blueberries with a fork. Sprinkle the starch over berries and stir to combine. If desired, add a pinch of salt.
Firmly press half of the oat mixture into the prepared pan, evenly tamping down. Evenly spread with the blueberry filling. Crumble remaining oat mixture over filling. Bake for 25 to 30 minutes or until filling is bubbly and topping is golden. Cool completely, in the pan, on a wire rack. Refrigerate until cold.