Preheat the oven to 350°F (175°C). Grease an 8x8-inch baking pan with coconut oil.
In a mixing bowl, whisk together the almond flour, coconut flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
In another mixing bowl, whisk together the eggs, sweetener, coconut oil, and vanilla extract.
Add the dry ingredients to the wet ingredients and mix until well combined.
Fold in the shredded carrots and chopped walnuts (if using).
Pour the batter into the prepared baking pan and smooth out the top with a spatula.
Bake for 25-30 minutes, until golden brown and a toothpick inserted into the center comes out clean.
Let the bars cool in the pan for 10-15 minutes, then transfer to a wire rack to cool completely.
Cut into 8 bars and serve. Store in an airtight container in the refrigerator for up to 5 days.