Preheat your oven to 180°C/350°F and grease and line a 9x9 pan with parchment leaving some overhang to easily pull it out after.
Combine the oats, chopped walnuts and almonds and the coconut on a baking sheet and toast them in the oven for 12 to 15 minutes, then set aside to cool a bit.
While those are toasting, in a saucepan combine the brown sugar, water, salt and coconut oil. Heat up just until the sugar has dissolved and the coconut oil has melted then set aside.
Whisk together the flour, baking powder and baking soda and set aside as well.
Stir the mashed bananas into the saucepan of sugar and coconut oil.
Add the toasted oats, nuts and coconut and stir until everything is evenly coated. Then add the flour mixture and stir just until incorporated.
Carefully stir in the chocolate chips to avoid them melting too much and transfer the mixture to your lined pan.
Spread it out evenly (no need to press it in) and bake for 25-30 minutes (still at 180°C/350°F).
Let it cool for a few minutes before pulling it out using the parchment and placing on a wire rack to cool completely.