Slice the polenta in half crosswise. Then slice each half into 6 rounds, about 1/2-inch thick, so that you have 12 rounds total.
Heat the canola oil in a large nonstick skillet over medium-high heat. Gently slide each polenta round into the hot oil using a spatula. If your pan is not large enough then fry 6 at a time. Fry until golden brown and cooked through, about 5 minutes per side. Remove from the oil and drain on a paper towel-lined sheet tray.
In a medium bowl, combine the beans, salsa and the 2 teaspoons hot sauce. Mash the beans with a fork or potato masher.
In a small bowl, combine the sour cream, remaining 1 tablespoon hot sauce and the lime juice and mix until well blended.
Build the sopes by spreading about 2 tablespoons mashed black beans on top of a fried polenta round. Top with a small amount of shredded lettuce and about 1 tablespoon of the salsa and drizzle with some of the sour cream mixture.