Combine the flour, soda, salt, and cinnamon. Add the dry ingredients to the egg mixture, 1 cup at a time.
Drain the raisins/dates and add them, along with the walnuts, to the dough. Mix thoroughly. The dough will be sticky. Oil your hands and make 2 or 3 loaves out of the dough.
Bake them on a greased cookie sheet at 350 degrees for 20-25 minutes. Slice the biscotti while they are warm. If you want them to be extra-crispy, place them on their sides and re-bake them for 5-10 minutes more.