Preheat the oven to 325° F. Line the baking sheet with a silicone mat or parchment paper. Set aside.
Lightly toast almonds and chop coarsely. Set aside.
Sift together the flour, baking powder, and salt in a medium bowl. Whisk everything well and set it aside.
Mix 2 tablespoon cornstarch with 4 tablespoon of water in a small bowl, and set aside.
In a bowl of a stand mixer fitted with a paddle attachment or an electric mixer, cream the butter and sugar on medium to high speed until creamy, light, and fluffy. Scrape down the sides and bottom of the bowl.
Add the cornstarch and water mixture, vanilla, and orange zest, and beat until everything is well combined. Scrape down the sides of the bowl again.
Add the dry ingredients and orange juice and mix on low speed to combine. Next, add the chopped almonds, and mix to distribute thoroughly. However, make sure not to overmix.
Place the dough onto a clean, lightly floured surface or baking mat. Divide the dough into two equal parts.
Place the dough balls into a prepared baking sheet. Shape each dough into a log, about 9 inches long and 2 inches wide.
Keep both logs on a baking sheet with at least 3 inches of space between them. If using a small baking sheet, bake one log at a time.
Bake in preheated oven for 25 to 30 minutes or until the top is firm to touch and a toothpick inserted into the center comes out clean.
Remove from the oven and allow to cool on the baking sheet. However, do not let the logs cool completely.
Carefully transfer the logs to a cutting board when they are still warm. Use the serrated knife to cut the logs into even diagonal slices. There will be a total of 26-28 slices.
Transfer the biscotti back onto a baking sheet, laying them flat and just a small space between them.
Return the biscotti to the oven and bake them again at 325° F for 15-25 minutes or until they begin to brown around the edges.
Because every oven is different, you may need to bake the biscotti a little longer than 15-20 minutes. Then remove from the oven and allow the biscotti to cool on the baking tray.
The biscotti can be kept in an airtight container for at least two weeks.