Place almonds in a food processor; process until finely ground. Set aside.
Beat butter at medium speed with an electric mixer until creamy; gradually add sugar, beating well. Stir in almond extract.
Combine ground almonds, flour, and salt; gradually add to butter mixture, beating at low speed until blended.
Roll dough to 1/2" thickness on a lightly floured surface. Cut with a 2 1/2" round cutter or Christmas cookie cutter. Place 2" apart on ungreased baking sheets.
Bake at 275° for 45 minutes. Cool 2 minutes on baking sheets. Remove to wire racks to cool.
Note: Toast natural almonds on a baking sheet at 350° for 6 to 8 minutes or until they smell fragrant. Then cool and grind almonds in a food processor until almost a powder consistency. We found that leaving the skins on the nuts adds a pleasing speckled appearance and rich flavor to the shortbread.