Adjust the oven rack to the middle position, pre-heat the oven to 350ºF (180ºC) and line two large baking sheets with parchment/baking paper.
You can prepare the cookie dough either by hand, using a wooden spoon, or using a stand mixer fitted with the paddle attachment on the lowest speed setting. I don't recommend using a hand mixer.
In a large bowl, whisk together the gluten free flour blend, sugar, xanthan gum and salt.
Add the softened butter and work it into the dry ingredients until you get a mixture resembling breadcrumbs. (If making the cookie dough by hand, use your fingertips to work the butter into the dry ingredients.)
Add the egg and vanilla, and mix well until everything comes together into a smooth, workable cookie dough that isn't sticky to the touch. It should be soft enough to roll out without cracking but also firm enough so you don’ t have to chill it first.
Give the cookie dough a knead to make sure it's perfectly smooth and shape it into a ball.
Roll it out on a lightly floured work surface until it's about ¼ inch (6-7mm) thick.
Cut out individual sugar cookies with cookie cutters of choice and transfer them to the lined baking sheets, spacing them about 1 inch (2.5cm) apart. Re-use any scraps by kneading them together and re-rolling. You should get about 36-40 cookies in total, but the exact number will depend on their size and thickness.
Bake at 350ºF (180ºC) for about 10-12 minutes or until they’re light golden around the edges. If you prefer crisper cookies, you can bake them a few minutes longer, until they’re more deeply golden brown.
Allow the cookies to cool on the baking sheet for about 10 minutes, then transfer them to a wire rack to cool completely before decorating.