Preheat the oven to 350°F and line two baking sheets with parchment paper. Set aside.

On a floured surface, roll out the cookie dough to 1/4 inch (5mm) thick, cut out as many snowflakes as you can, and place on the prepared baking sheets, about 1-inch (3cm) apart.

Bake the cookies for 10-12 minutes, rotating the pans halfway through, until the surface looks dry. Transfer the cookies on the wire racks to cool completely.

Once completely cool, place the cookies on a work surface or baking sheet.

Set up bowls of sprinkles, sanding sugar, or dragees nearby.

Place a small amount of royal icing in your piping bag and check the consistency by piping a line of icing onto a plate. It should pipe smoothly and hold its shape. If it is too thick and doesn’t pipe smoothly, stir in a few drops of water and test again. If it runs, stir in a teaspoon or two of powdered sugar and test again.

Once the consistency is correct, you can go ahead and fill your piping bag.

Working with one cookie at a time, pipe a large dot of icing in the center of the snowflake. Then, from the dot, pipe a line of icing down the center of each arm of the snowflake. Pipe a few small v-shaped branching details from the centerline of the icing arms to the edge of the cookie.

Finally, before the icing has been set, add sprinkles, sanding sugar, or dragees to the cookie. Set aside while you decorate the remaining cookies.

Allow the icing to dry completely before storing the cookies in an airtight container at room temperature for up to 3 days.