Preheat the oven to 350°F / 180°C. Line a baking sheet with parchment paper and set aside.
In a large bowl, stir together the rolled oats, cinnamon, baking soda, sea salt, almond flour, and brown rice flour until combined.
In the bowl of a food processor, combine the mashed banana, almond butter, maple syrup, ground flaxseed, coconut oil, and vanilla. Process on high until the mixture is smooth.
Scrape the almond butter mixture into the large bowl with the oats and flour mixture. Throw your add-ins into the large bowl. Stir the mixture with a spatula until you have a unified and very stiff cookie dough.
Drop 2 tablespoons of dough per cookie onto the prepared baking sheet. Flatten each mound of dough with the palm of your hand. Slide the baking sheet into the oven and bake until lightly golden brown, about 15 to 17 minutes.
Cool cookies completely before storing in an airtight container. These will last on the counter for 5 days. You can also wrap each cookie individually with plastic wrap and freeze them. I place all the wrapped cookies in a resealable bag and defrost them as needed.
I tested these as oil free by omitting the coconut oil and they turned out great.
I used pecans instead of walnuts.
Nutrition facts do not take the 1 cup of add-ins into account as this would vary depending on what is used.