In a small bowl, whisk flaxseed and water. Let sit for about 10 minutes while you are getting other ingredients ready.
Preheat oven to 350 degrees F, line large baking sheet with unbleached parchment paper and spray with cooking spray.
In a large bowl, mash bananas. Add coconut oil, vanilla extract, cinnamon, baking soda and salt. Add flaxseed mixture and whisk really well. Add oats and oat flour; stir to combine. Add nuts and dates; mix well. Dough will be very thick.
Using a large ice cream scoop, place batter on previously prepared sheet and flatten with the back of a scoop into large size cookies. Cookies do not spread, you should be able to place 6 large cookies per sheet. Bake for 20 minutes or until nuts start to brown a bit.
Remove from the oven and let cookies cool for a minute, then transfer onto a cooling rack to cool off completely. Enjoy for breakfast, snack or dessert!