Preheat oven to 350°F and line a baking sheet with parchment paper.

In a medium bowl, sift together the almond flour, oat flour, tapioca flour, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment or a mixing bowl with a hand mixer, cream the butter and sugar together on medium high speed until light and fluffy, 3-5 minutes.

Add the egg and vanilla, mixing just until combined, scraping down the sides and bottom as needed.

With the mixer on low, slowly add the dry ingredients. Increase the speed to medium and mix until just combined, scraping down the sides as needed.

Roll the dough out on a surface dusted with oat flour into a ½ inch thick round and cut out circles with 2.5-inch round cutter or glass. Alternatively, roll about 2 tablespoons of dough into a ball and flatten into a ½-inch thick 2.5-inch wide circle. Place cookies 2 inches apart on the baking sheet.

Bake for 12 minutes (for nut-free variation, bake only 10 minutes). Remove from oven and let cool for 5 minutes on the baking sheet before using a thin spatula to transfer to a wire rack to cool completely.

Meanwhile prepare the frosting. In the bowl of a stand mixer fitted with the paddle attachment or a mixing bowl with a hand mixer, beat the butter on medium speed until smooth, scraping the sides as you go.

With the mixer on low, slowly add the powdered sugar, ground freeze-dried strawberries, vanilla extract, and salt. Beat until smooth. Add the heavy cream or milk, starting with 3 tablespoons, until the frosting is smooth enough to spread.

Once cookies are cool, spread 2-3 teaspoons of frosting onto each cookie and decorate with sprinkles.