Preheat oven to 350°F. Line a baking sheet with parchment paper or greased foil. Set aside.
In a small bowl, make the flax “egg” by combining the ground flaxseed with the water. Whisk to combine and set aside to thicken.
In a medium bowl, combine the oat flour, tapioca starch, pumpkin pie spice, baking powder, baking soda, and salt. Whisk to combine.
In a large bowl, combine the pumpkin puree, brown sugar, coconut oil, maple syrup, apple cider vinegar, and vanilla. Whisk together until smooth.
Add flax “egg” to the pumpkin mixture and whisk to combine.
Add the oat flour mixture to the pumpkin mixture and stir to combine. Until no flour streaks remain. Then fold in the chocolate chips.
Using a 2 tablespoon scoop, scoop cookie dough onto the prepared baking sheet, leaving about 2 inches of space between each cookie. I was able to fit 6 cookies on to my half-size baking sheet.
Bake in the preheated oven for 12-13 minutes. Be careful not to overbake these or they'll be crumbly and dry.
Let cool on the baking sheet for 5-10 minutes before transferring to a cooling rack. Store leftovers in a lidded container on the counter for up to a week.