To make almond biscotti, begin by preheating the oven to 350 degrees Fahrenheit. In a large bowl, whisk together 2 1/2 cups of all-purpose flour, 1 cup of sugar, 2 teaspoons of baking powder and 1/4 teaspoon of fine salt.
Beat 3 large eggs and 1 tablespoon of pure vanilla extract with an electric mixer until combined. Add 1 cup of toasted, slivered almonds, and beat until combined. Line a rimmed baking sheet with parchment paper, and transfer half of the dough to the parchment paper. Form the dough into a 2 1/2 inch wide by 3/4 inch tall log. Repeat this step with the other half of the dough. The dough can be sticky, so lightly coat your hands in cooking oil or flour before forming the logs if necessary. Make the logs as uniform as possible to ensure even baking.
Bake the dough 20 to 25 minutes, rotating the baking sheet halfway through, until the dough is firm but gives when pressed. Let it cool on the baking sheet or a wire rack for 20 minutes. Using a serrated knife, cut the dough into 1/4 inch diagonal slices and arrange cut side down on two parchment-lined baking sheets. Bake about 15 minutes, until the biscotti are crisp and golden. Rotate the baking sheet and flip the biscotti halfway through baking. Let them cool on sheets or wire racks before serving. The biscotti can be stored for two days in an airtight container or frozen for three months.