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

In the bowl of a stand mixer fitted with the paddle attachment or a large mixing bowl with a hand mixer, cream the butter and dark brown sugar until fluffy and light in color, 2-3 minutes, scraping down the sides as needed.

Mix in the molasses until well combined, followed by the egg and vanilla extract, scraping down the sides as needed, mixing until well combined. Don't be alarmed if the mixture seems to separate after you add the egg. It will come back together with the dry ingredients.

With the mixer on low, slowly add the dry ingredients, scraping down the sides and bottom of the bowl as you go, mixing, until completely incorporated.

Divide the dough into two equal pieces. Roll out half of the dough between two pieces of parchment paper, until ⅛ to ¼-inch thick. Keeping the dough sandwiched between the sheets of parchment paper, place it on a baking sheet and freeze flat for 15 minutes (or refrigerate for an hour). Repeat with the second half, stacking it on top of the first in the freezer.

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

Working with one half at a time, peel off one sheet of parchment paper, leaving it on top of the dough, then flip it over and peel off the other half (so you still have a sheet of parchment paper underneath, but it has been peeled off the frozen dough already). Use cookie cutters to cut out your shapes. Transfer your cut cookies to a parchment-lined baking sheet as close together as possible. Roll the scraps up between the two sheets of parchment paper and cut out more cookies, pausing only to rechill any rolled-out dough sheets for 5-10 minutes that get too soft to work with, as needed. Chill the cut cookies on a parchment-lined baking sheet in the fridge for 30 minutes or in the freezer for 15 minutes. While the first half of the cut cookies chill, repeat above by cutting out the second half. While the second batch of cut cookies chill, begin baking the first batch.

Working in batches, transfer the frozen cookies to a parchment-lined baking sheet 1.5 inches apart. Note: Divvy them on baking sheets based on the size of the shape. Smaller shapes take less time to bake, so separating by size will keep the little ones from overbaking while the larger shapes bake through. One sheet at a time, bake the cookies for 5-7 minutes, until just set and puffy, but the center still looks ever-so-slightly underbaked. Smaller cookies, 2-3 inches, will take just 5-5.5 minutes and larger 4-inch cookies will take 6.5-7 minutes. For cakier cookies add 1 minute to the bake time, and for crispy cookies add 2-3 minutes to the bake time.

Let the cookies cool on the baking sheet for 2-3 minutes before using a thin metal spatula to transfer them to a wire rack to cool completely before icing. Repeat until all the cookies are baked!

While the cookies cool, make the icing. In a medium bowl, whisk the powdered sugar with just 1 tablespoon of milk, corn syrup, vanilla, and salt until smooth. Add another few drops of milk at a time until the icing is the proper consistency. To pipe decorations that don't pool on your cookies, the icing should be very thick, but still able to be piped. When you lift the whisk up and drizzle icing back into the bowl, the stream should just barely sit on top, before every so slowly incorporating back in. Fill a small pastry bag fitted with a small round tip with icing and decorate the cooled cookies to your heart's content. Let sit for 10 minutes until the icing sets.