Line a sheet pan with parchment paper.
Sift together the flour and baking soda.
Whip the eggs, sugar, salt, and extract in an electric mixer on high speed with the wire whip until thick and light in color, about 5 minutes. Mix in the dry ingredients on low speed just until incorporated.
Add the almonds and anise seeds by hand and blend until evenly combined.
Form the dough into a log 4 by 16 in (10 by 41 cm) and place it on the prepared sheet pan.
Bake at 300°F/149°C until light golden brown and firm, about 1 hour. Lower the oven temperature to 275°F/135°C. Remove the pan from the oven and cool for 10 minutes.
Using a serrated knife, cut the log crosswise into slices ½ in (1 cm) thick. Lay them flat on the sheet pan and bake, turning the biscotti once halfway through, until golden brown and crisp, 20 to 25 minutes total.
Transfer the biscotti to wire racks and cool completely.