In a sizable mixing bowl, thoroughly combine the flour or matzo cake meal, potato starch, almond flour, half a teaspoon of cinnamon, and sea salt to create the dry mixture.

Using a stand mixer fitted with the paddle attachment, cream together the softened butter or coconut oil with 1 cup of sugar until smooth. Gradually add each egg, mixing well after each addition. Then gently fold in the dry mixture along with the slivered almonds, vanilla extract, and the fresh zest from the oranges until blended.

Divide this dough into two equal sections and place each section onto a long strip of parchment paper, shaping them into logs that are around 10 inches long and 2 inches wide. Press the top gently with your hand to flatten slightly, then seal the logs by twisting the ends of the parchment. Refrigerate these logs for at least an hour.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper. After chilling, remove the logs from the fridge, unwrap them, and place them side by side on the sheet. Bake for 35 to 45 minutes, just until they lightly brown and are not overly cracked on top, as a slight underbaking contributes to better texture.

Once the logs have completely cooled, wrap them securely in plastic wrap and freeze them for at least an hour. This will make slicing simpler and help prevent crumbling.

When you are prepared to continue, heat the oven again to 350°F and prepare two baking sheets with parchment. In a small bowl, mix the leftover cinnamon with 1/4 cup of sugar.

Remove the frozen logs, slicing them into approximately 1/2-inch thick pieces using a sharp serrated knife. Discard any end pieces that crumble apart. If the logs have been frozen for an extended period, allow them to rest for a few moments at room temperature before slicing.

Coat both sides of each cookie slice in the cinnamon-sugar mixture, and arrange them with the cut side facing down on the prepared sheets. Bake for 10 to 15 minutes, flip each cookie carefully, and continue baking for another 10 minutes or until they are golden and crisp. Allow to cool before serving to appreciate that perfect crunch.