Preheat the oven to 325 degrees F (162 C.) Line two baking sheets with parchment paper and set them aside. Arrange the oven racks on the middle and upper bottom sections of the oven.
To prepare the dry ingredients, in a large bowl, combine the old-fashioned rolled oats, oat flour, ground flax seeds, chia seeds, baking powder, cinnamon, and salt. Set it aside.
For the wet ingredients, in a separate medium bowl, combine the applesauce (or mashed bananas), coconut oil, maple syrup, and unsweetened almond milk. Stir until fully combined.
Add the wet ingredients into the dry ones, scraping the sides of the bowl as you mix until everything is evenly incorporated.
Using a rubber spatula, fold the walnuts and raisins into the batter. At this point, the batter will appear to be too wet*, but some moisture will be released while resting both during and after the baking process.
Using an ice cream scoop, scoop the dough and place each portion on the baking sheet, making sure that they are 1 inch apart from each other. Using the back of a spatula, gently press on top of each cookie to flatten them slightly. Also, we recommend dividing the cookies among two sheets to ensure they have equal air circulation in the oven.
Place the sheet pans in the middle and upper bottom rack and bake for 18-20 minutes or until the cookies turn lightly golden brown with crispy edges. Halfway through the baking process, turn the baking sheets from front to back and also switch them from top to bottom. With this being said, you can bake the cookies one sheet at a time if you prefer (please see notes, section "Bake in small batches.")
Remove from the oven and let the cookies rest on the baking sheets for 5 minutes. Then, transfer them to a cooking rack and let them cool for 15-30 minutes before serving.