In a large mixer bowl beat the butter with an electric mixer on medium to high speed for 30 seconds. Add 1/2 cup sugar and beat until well combined. Add egg yolk and almond extract. Beat until thoroughly combined. Beat or stir in the flour.
Season 2-1/2-inch sandbakkelse molds, if necessary. Place about 2 teaspoons of dough in center of each seasoned mold. Press dough in an even, very thin layer along the bottom and up the sides. Place molds on a cookie sheet. (Or, shape dough into 1-inch balls. Place 2 inches apart on an ungreased cookie sheet. Using a cookie stamp or bottom of a glass dipped in sugar, flatten balls to 1/4-inch thickness.)
Bake in a 375 degree F oven 8 to 9 minutes or until edges are lightly browned. Cool molded cookies in molds on a rack. To remove, invert the molds and tap lightly. If necessary, loosen edges of cookies. Cool completely on a wire rack. For stamped cookies, after baking remove to a wire rack to cool completely. Makes 24 cookies.