Preheat oven to 350°F (175°C) and line or lightly grease a muffin tin.
Mix grated carrots, Greek yogurt, honey, eggs, and vanilla in a large bowl until well combined.
Whisk almond flour, rolled oats, baking powder, baking soda, cinnamon, nutmeg, and salt in another bowl.
Add the dry ingredients to the wet mixture and stir gently until just combined, folding in walnuts if using.
Divide the batter evenly into muffin cups, filling each about ¾ full.
Bake 18 to 20 minutes until the tops are lightly golden and a toothpick inserted in the center comes out clean.
Cool in the pan for a few minutes, then transfer to a wire rack to finish cooling.