Preheat oven to 350 and line a baking sheet with parchment paper.
In a large bowl, mix together the oats, almond flour, and flaxseed meal. Push these ingredients off to the side to make room for the wet ingredients.
In the same bowl, add the mashed banana, oil, eggs, and vanilla to the open side of the bowl. Gently whisk the wet ingredients and then fully mix in with the dry ingredients. Batter should be thick so it holds its shape, but not too thick like cookie dough (see notes).
Fold in the chocolate chips.
Scoop mixture onto prepared cookie sheet in 2" mounds. You should get 12 cookies from the mix.
Bake for 18-20 minutes, or until lightly golden brown.
Bananas provide a different level of liquid pending on how ripe they are. If your bananas are super ripe and the batter seems to "liquidy" you can add a few more tablespoons of oats or almond flour. I typically don't need to add any more than the recipe says though.
I like using previously frozen and then thawed bananas, but ripe bananas straight from the counter also work.
In order to keep these 100% clean, you can skip the chocolate chips altogether or could add in 2-3 tablespoons of pure maple syrup if you'd like to sweeten them up.
I use certified gluten-free oats as I'm gluten-free, but if you aren't gluten-free, oats that aren't certified gluten-free will work too.