Mix all ingredients together by hand in a large bowl, except for the egg whites.
If the dough feels too crumbly, carefully add small amounts of egg whites until the dough is easier to roll into a large ball.
Lighlty cover your workspace and rolling pin with gluten-free flour.
Roll out the dough evenly (about 1/4 thick) and cut out your cookies with your cookie cutters of choice.
Place your cut-out cookies on a baking sheet lined with foil and chill for about 10 minutes in the refrigerator. Note: this is extremely important! If you don't chill them, they will expand and lose their shape once you bake them.
375°F for 10 minutes, or until edges are golden. Set aside and allow them to completely cool before decorating.