Preheat the oven to 180ºC and prepare a baking sheet (with baking paper, or lightly greased).
In a medium bowl, beat the mashed banana, peanut butter, flax egg, melted coconut oil and sugar until smooth.
Add the oats, oat flour, cinnamon, salt and bicarb and mix thoroughly.
Spoon small dollops (a heaped teaspoon each) onto the baking sheet, spaced a couple of centimetres apart.
Bake for 10-12 minutes, until the edges are golden-brown.
Remove and cool on a wire rack.
Store in an airtight container.