Preheat your oven to 350 degrees Fahrenheit and line an 8x8 inch baking pan with parchment paper, leaving a bit of an overhang on the sides.

In a large mixing bowl, peel your three ripe bananas and begin mashing them with a fork. You want a relatively smooth consistency, but a few small lumps are perfectly fine.

Add in half a cup of your chosen nut butter and a teaspoon of pure vanilla extract. Stir these into the banana mash until the mixture is cohesive and creamy.

Gently stir in two cups of rolled oats, a teaspoon of ground cinnamon, and a pinch of sea salt. If you are adding walnuts or chocolate chips, fold them in now.

Transfer the batter into your prepared pan. Use the back of a spoon or a damp spatula to press the mixture firmly and evenly into the corners.

Place the pan in the center rack of your oven. Bake for 18 to 22 minutes. You aren't looking for a deep brown color, rather, you want the edges to be set and the top to feel firm to a light touch.

Allow the pan to cool completely on a wire rack. Once fully cooled, slice them into squares and store them in an airtight container.