Brush a 12", non-stick pizza pan with the olive oil and set aside. Pour the water into a medium-sized, heavy-bottomed pot and bring to a boil over medium-high heat. Add the salt, and then reduce heat to medium. While whisking steadily, slowly pour in the cornmeal. Lower heat to medium low and cook the cornmeal 5 minutes, whisking frequently. Cook 15 minutes more, but, now that it has begun to thicken, use a sturdy wooden spoon to stir the polenta frequently. At this point the polenta will be quite thick, but spreadable. Spoon the polenta on to the pizza pan and quickly spread into a circle that's about 1/4-to 1/2" thick. Allow the polenta to cool to room temperature and set. (Pizza could be made to this point several hours in advance; cover and refrigerate until needed.) Remove the sausage from its casing, pull into small nuggets, and set in a non-stick skillet. Set over medium-heat and cook until the sausage is cooked through. Remove from the heat and drain the sausage on paper towels. Preheat the oven to 450 degrees F. Spread the tomato sauce on the polenta. Top with cheese, olives and sausage. Sprinkle the pizza with the fennel seed. Bake for 12-15 minutes, until the polenta is hot and a little crispy on the bottom. Cool a few minutes, top with fresh basil, cut into 8 wedges, and serve.