In a small bowl, whisk together the gluten free flour, baking powder, and salt.
In the large bowl of a stand mixer using the paddle attachment, mix the melted coconut oil, sugar, eggs, and vanilla extract. Add the dry ingredients to the bowl and mix until a uniform dough forms.
Scrape the dough onto a large piece of wax paper. Shape the dough into 2 disks and wrap it in the wax paper. Transfer the dough to the refrigerator, and refrigerate it for 30 to 40 minutes.
Preheat the oven to 350 degrees and set the rack in the center of the oven.
Remove one disk of the dough from the refrigerator and place it on a floured work surface. Roll the dough to a thickness of 1/4 inch (any thinner than that will yield crispy cookies). Add a tablespoon of flour to the dough if necessary to roll it out without having the dough stick to the rolling pin.
Cut the cookies into shapes using 2- to 3-inch cookie cutters. Place the cookies on a parchment-lined cookie sheet and bake for 8 to 9 minutes, until the cookies are set. Bake one cookie sheet at a time in the center of the oven. Continue with the second disk of dough once the first disk is done, but leave the dough in the refrigerator until you’re ready to roll it.
Remove the cookies from the oven, and carefully transfer them to a cooling rack.
While the cookies are cooling, make a simple syrup by boiling 2 tablespoons of sugar and 3 tablespoons of water in a small pot. Stir until the sugar is dissolved (a couple minutes).
Once the cookies have cooled, brush the cookies one at a time with the simple syrup. Quickly add the sprinkles or decorating sugar to each cookie before the simple syrup solidifies so the decorations will stick.
Store in an airtight container at room temperature for up to 5 days, or freeze for later.