Preheat the oven to 350ºF and line a cookie sheet with parchment paper.
In a large bowl, beat the egg whites with the salt frothy. Add the sweetener and almond extract, and continue to beat until they hold soft peaks. Do not over-beat.
Gently fold in the almond flour with a rubber spatula, until just combined. The dough should be quite sticky.
Roll the mixture into balls about 1 ½ inches in diameter - you should get about 20 balls. If the dough is very sticky, you can wet your hands slightly to roll the balls. Place on the prepared baking sheet a few inches apart.
Press them down to about 1 inch thick with the palm of your hand. Then press an almond slice into the top of each cookie.
Bake 15 to 20 minutes, or until just turning golden brown on the edges. Remove and let cool completely on the pan.
Dust the cookies lightly with powdered sweetener.
