Preheat oven to 350 degrees F. Line a baking sheet with parchment paper or a silicone mat.
Prepare flax egg in a large bowl by mixing the ground flaxseed and water until combined. Let it sit for 5 minutes to thicken.
In another medium bowl, combine the almond flour, coconut flour, arrowroot or cornstarch, baking powder, and salt. Whisk until well combined.
In the bowl of the flax egg, add the melted coconut oil, sugar, maple syrup, vanilla extract, and almond extract. Whisk until well combined.
Add the dry ingredients to the bowl of the wet ingredients. Use a spatula and stir until well combined. Let it sit for 5 minutes. This helps the flours to absorb the moisture.
Make cookie balls by rolling about 1.5 Tbsp of dough with your hands. Place on the cookie sheet. Take the bottom of a glass cup (or use your hands) and flatten the cookie balls (they don’t spread). Bake for 8-10 minutes, until lightly golden. Don’t overbake! They will firm up more as they cool. Let them cool on the pan for 10-15 minutes, then transfer to a wire rack to cool completely. Make sure you cool the cookies completely before frosting.
To make the frosting, beat butter and sugar on high until fluffy, about 2 minutes. Add vanilla extract and beat until smooth and fluffy. To make it thicker, add more powdered sugar. To make it thinner, add a teaspoon of almond milk at a time until your desired consistency.
Frost each cookie however you want! Enjoy! Store leftover cookies in an airtight container on the counter.
Notes
Inspired by Ambitious Kitchen's soft almond flour sugar cookies