In a large mixing bowl, combine almond flour, sugars and salt.
Add the egg whites and almond extract and mix with a whisk. It will become crumbly and at this point you can continue mixing with your hands until you form a cohesive ball.
Cover the bowl with plastic wrap and refreigerate for about 1 hr.
Preheat the oven to 325ºF.
Line a cookie sheet (or two) with parchment paper. Place icing sugar in a wide bowl.
Using a teaspoon, scoop dough and shape into 1 inch balls. Once you have 5 or 6 balls of dough in the shallow bowl, shake it and rotate it so the bowls get completely covered in icing sugar. Scoop them into a colander and roll gently over the shallow bowl to release the extra sugar. Place the balls onto the lined cookie sheet. Repeat the process until all the dough is fromed into balls.
Arrange the balls of dough on the cookie sheet at a distance of about 1 inch from each other. Press gently with the bottom of a glass or any other utensil that might do the trick.
Place in the oven and bake for about 18 minutes (as always, check a few minutes before to make sure they are not baking too much). The cookies will crackle slightly and will turn golden brown under the sugar.
Remove the tray from the oven, let rest for a few minutes and transfer the cookies to a rack to cool. The cookies will be a bit soft and chewy the first day or two. Let them dry until they become very crunchy if you want to use them to make pie crust.