Mash the banana in a mixing bowl and add maple syrup, applesauce, coconut oil and vanilla extract.
Mix well using a hand mixer.
Add the oats, cinnamon and salt, mix until well combined. The mixture will be quite moist.
Transfer the base layer into the square pan. Smooth it out with a spatula until nice and even. Bake for 11 minutes.
In the same mixing bowl, combine all the ingredients for the topping until well combined. Remove the pan from oven.
Pour topping mixture over the base and spread it out evenly.
Press it down into the base layer with a spatula or cover it with parchment paper while you are pressing it down with your hands. If using the method with the parchment paper remove the paper before putting the tin into the oven again.
Bake for an additional 20 minutes.
Allow the bars to cool and set before slicing the squares.
The bars can be stored in the refrigerator for up to a week.