Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the whole wheat flour (or almond flour), baking soda, and salt. Whisk these dry ingredients together until they are evenly mixed.
In another bowl, mix the melted coconut oil and mashed banana until smooth. Stir in the vanilla extract until well combined.
Gradually add the wet mixture to the dry ingredients, stirring until just combined. Be careful not to overmix.
Fold in the sugar-free chocolate chips and chopped walnuts, if using, ensuring they are evenly distributed throughout the dough.
Using a spoon or cookie scoop, drop rounded tablespoons of dough onto the prepared baking sheet, leaving space between each cookie as they will spread slightly.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked; they will continue to firm up as they cool.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.