Line a cookie sheet with parchment paper. Sift together the flour and baking soda. Whip the eggs, sugar, salt and anise extract in an electric mixer using the whip attachment on high speed, until thick and light in color, about 5 minutes. On low speed, mix in the dry ingredients until just incorporated. Add the almonds and anise seeds by hand and blend until evenly combined.
On a parchment-lined cookie sheet, form the dough into a 4-by-16-inch-wide flattened log (about 3/4 to 1 inch high).
Bake in a 300 degrees F oven until light golden brown, about 1 hour. Remove the pan from the oven and let cool for 10 minutes. Lower the oven temperature to 275 degrees F.
Using a serrated knife, cut the strip crosswise into 1/2-inch slices. Lay the sliced cookies back on the parchment-lined cookie sheet and bake, turning the biscotti once half-way through the baking time, until golden brown and crisp, 20 to 25 minutes. Cool the cookies on a wire rack and store in an airtight container for up to 2 weeks (or longer, if well stored).