Cream unsalted butter and sugar in a large bowl until light and fluffy.
Beat in egg and almond extract.
Combine flour, salt, and baking soda in a separate bowl.
Add to creamed mixture and beat until thoroughly combined.
Take a heaping tablespoon of dough and roll it into a ball (approximately 1" to 1-1/4" in size). Place a couple of inches apart on parchment-lined baking sheets.
Gently flatten with the bottom of a small bowl.
Sprinkle each cookie with sliced almonds, gently pressing almonds into the dough.
Optional: Sprinkle white sugar over cookies before or after baking.
Bake for 14-15 minutes or until edges and bottoms are lightly browned. Cool for a few minutes before transferring to wire racks to cool completely.