Preheat oven to 300degreesF. Line 2 baking sheets with parchment. Combine dry ingredients and set aside. Whisk the eggs, amaretto (if using, or the almond extract and rum), vanilla and anise extracts in your mixer until well blended. Add the dry ingredients and mix until combined. Dough should be thick and sticky at this point--do not worry, and DO NOT add more flour! Scrape the dough out onto a parchment lined sheet pan. Flour your hands and shape into a long flat loaf about 10 inches long and 5 inches wide. This will be kind of messy, so don't worry about how neat it is, just try to get it in that general shape. Bake until firm and dry, about 50 minutes. Remove from the oven and cool 10 minute. Use a long serrated knife and slice into 1/2-inch wide slices. Lay the slices cut side down on the baking sheet and bake another 20 minutes. Turn the slices over and bake 20 minutes more, or until the cookies are a light golden brown. Cool the biscotti on a rack; cool completely before storing.