Preheat the oven to 300ºF. Line a baking sheet with parchment and spray with nonstick spray.
Use a high-powered blender to process the oats into flour. Pour the oat flour into a mixing bowl and add the baking soda, cinnamon, nutmeg and ginger.
Put the bananas into the blender and blend until completely smooth. Add to the oat mixture along with the sunflower seeds and raisins or currants, and mix until well combined.
Use a 1-ounce cookie scoop to place spoonfuls of the cookie dough on the baking sheet. Dip the scoop in water to keep the dough from sticking. Use lightly moistened fingers to flatten each cookie down slightly. Bake 15 minutes.
Cool cookies on a wire rack and store in an airtight container. Makes about 24 cookies.