If using polenta from a tube, skip to step 2. For instant polenta, bring 3 cups salted water to a simmer in a pot on medium heat. Slowly add the instant polenta, constantly stirring to ensure that clumps do not form. Continue stirring for 4 to 5 minutes until the polenta becomes very thick. Lightly grease a baking sheet and pour the polenta evenly into the pan so that it is approximately half an inch thick. Place the pan in the fridge for 45 minutes until it is hard. Once hard, remove form the fridge and cut into circles using a knife or cookie cutter.