Fill a saucepan with the water and place on the heat.
When it begins to tremble, shortly before it begins to boil, add the salt.
When the water begins to boil, slowly add the corn flour and stir to prevent lumps.
For wheat flour, use twice the water.
Keep stirring the polenta with a wooden spoon in the same direction and if the mixture tends to harden too quickly, add hot water.
After about 40 minutes, the polenta will begin to be cooked, as it will begin to detach from the side of the pan.
Continue cooking for another 10 or 20 minutes, depending on taste.
When it is ready, turn over the polenta out onto a cutting board, spreading it out so that it will cool more quickly.
Wait for it to cool slightly before cutting it with a string or a thread of cotton in order to obtain clean cuts and compact slices.