Set oven at 450° and grease and flour baking sheets. Cream almond paste with melted butter. Beat egg whites with salt until they hold soft peaks. Add sugar, a tablespoon at a time. Continue beating until meringue is very firm. Fold into almond paste mixture, adding flour and slivered almonds. Drop small rounds of batter on prepared baking sheets, leaving 1 inch between cookies. Bake 5 to 8 minutes, or until edges of cookies are golden brown. Yields approximately 30 cookies.