Preheat oven to 350 degrees, and line a baking sheet with Silpat or parchment paper.
Beat egg whites until stiff peaks form. Set aside.
Cut almond paste into one-inch cubes. Add to the bowl of an electric stand mixer along with granulated sugar and powdered sugar. With the paddle mixer, beat until the texture is sandy.
Add flour, salt, and almond extract and mix. Then add beaten egg whites, and mix on low speed until a dough forms.
Scoop dough into rounded tablespoon-sized balls, and coat with sliced almonds. Place on lined baking sheet, and bake at 350 degrees for 20 minutes, or until the edges are golden.