Toast almonds and allow to cool completely
Whisk together flour, baking soda, and salt.
Beat together butter, sugars, corn syrup, vanilla, and almond extract in a large bowl with an electric mixer at medium-high speed (use paddle attachment if you have a stand mixer) until pale and fluffy, about 2 minutes.
Reduce speed to low, then add flour mixture and mix just until a dough begins to form. Add almonds and mix just until incorporated.
Form dough into a rectangular log (about 12 inches long, 2 inches wide, and 2 inches thick). Wrap in wax paper and chill until firm, about 2 hours.
Put oven rack in middle position and preheat oven to 325°F. Butter a large baking sheet.
Cut half of log into 1/8-inch-thick slices with a thin sharp knife and arrange 3/4 inch apart on baking sheet. (Keep remaining dough chilled.)
Bake cookies until golden, about 12 minutes, then transfer with a thin metal spatula to a rack to cool.
Repeat with remaining dough.
Dough can be chilled up to 2 days, or frozen, wrapped also in plastic wrap, 1 month. Transfer frozen dough to refrigerator to thaw slightly at least 2 hours before slicing.
Cookies can be baked 3 days ahead and cooled completely, then kept in an airtight container at room temperature.