Beat butter and 2/3 cup sugar at medium speed with an electric mixer until light and fluffy. Gradually add flour, beating at low speed until blended.
Divide dough into 6 equal portions, and roll each dough portion into a 12-inch-long x 1-inch-wide strip. Place 3 dough strips on each of 2 lightly greased baking sheets.
Make a 1/2-inch-wide x 1/4-inch-deep indentation down center of each strip, using the handle of a wooden spoon.
Bake, in 2 batches, at 350° for 15 minutes. Remove from oven, and spoon jam into indentations. Bake 5 more minutes or until lightly browned.
Whisk together powdered sugar, 3 1/2 tablespoons water, and almond extract; drizzle over warm shortbread. Cut each strip diagonally into 12 (1-inch-wide) slices. Cool in pans on wire racks. Store in an airtight container.