Add in almond flour, arrowroot, tapioca, and salt. Use mixer on high speed until dough forms.
Knead dough (it will be a bit sticky, you can use a bit of arrowroot or tapioca flour to help) and separate into two balls. Place back in mixing bowl, cover with plastic wrap or towel, then put in refrigerator for at least an hour.
Take dough out of refrigerator. Place either arrowroot or tapioca flour on parchment paper placed on cookie sheet.
Roll out dough to about 1/4 inch thickness. Use cookie cutters to cut out shapes directly on parchment paper so you do not need to transfer them to cookie sheet.
Place cookies in oven and bake for about 8-10 minutes. Cookies will be slightly brown around edges.
Icing
Melt 2 tbsp. of butter till very soft but not liquid.
Add dash of vanilla and ½ cup of powdered sugar. Mix with a fork until smooth.
Add food coloring of choice and mix until color is even.
Use spreader or small knife to spread icing on cooled cookies.
Add sprinkles or any topping of choice. Let sit for a few minutes until icing slightly hardens up.
FYI, each batch of icing should decorate about 12 cookies.