Beat the Butter (1 cup) until smooth and creamy. It is better to use an electric mixer if you have one.
Add the Powdered Confectioners Sugar (8 tablespoon) and Vanilla Extract (1 teaspoon) and beat until smooth, about 2 minutes.
Gently stir in the All-Purpose Flour (2 cup) and mix until incorporated.
Wrap the dough in plastic wrap and refrigerate for at least 1 hour or more if needed.
On a slightly floured surface, roll out the dough to a 0.5-centimeter thickness, and cut out 3-centimeter by 2-centimeter rectangles to make a flag shape. Place on a baking sheet and refrigerate for 20 to 30 minutes.
Preheat oven to 350 degrees F (180 degrees C). Meanwhile, prepare the frosting by combining the Powdered Confectioners Sugar (2 cup) with a few tablespoons of Water (to taste), just enough to obtain the desired density.
Divide the icing into 3 bowls, leave one white and add Blue Food Coloring (to taste) to one of the other bowls.
Add Red Food Coloring (to taste) to the last one. Put the icings into squeeze bottles.
Bake the cookies for about 10 minutes, then let them cool down completely.
Then, pipe even lines on each cookie, alternating between the white and red icing.
When you reach half of the cookie, pipe out a square in the top left using the blue icing.
Then, finish up with more lines on the right side.
Let the icing dry completely before storing. Enjoy!