Preheat oven to 375ºF (static) or 350ºF (convection).
Cream butter and sugar (or half of gfJules Sugar Cut-Out Cookie Mix) until very fluffy.
Add egg (or egg replacer), vanilla extract and milk, beating until integrated. Add the remaining mix or dry ingredients last, beating just until dough is holding together. Add slightly more milk if needed to keep dough from being crumbly.
Gather dough and form a flat disc.
Dust a silicone baking mat or parchment paper taped to your counter with gfJules All-Purpose Gluten-Free Flour. Dust a rolling pin and cookie cutters with Jules Flour as well. Roll the dough from the center in each direction to form a circle at least 12 inches across and 1/4-inch thick (see photo of cut cookie for appropriate thickness).
Using a butter knife or pastry cutter, cut the uneven edges of the rolled dough off so that you are left with a clean rectangle or circle of dough. Gather the cut off edges of the dough together and re-roll on a separate piece of parchment, then use cookie cutters to make cookies with remaining dough.
Slide the parchment or silicone baking mat onto a flat cookie sheet. Arrange any cut cookies on a separate baking sheet lined with parchment. Bake cookies for 8–10 minutes, but remove before they begin to brown at the edges. Bake the large flag cookie for 13-14 minutes – the dough should still be soft, not browned or crispy.
Remove to fully cool on a wire rack.