In a bowl, place the milk, yogurt and stir well, then cover the bowl and place in the oven turned OFF and leave for 12 hours.
OBS.: The liter of milk must be in a bag and not in a box.
But if you can't find it in a bag, you can try to make it with the box, now I don't know if it will have the same consistency.
After 12 hours take it to the fridge for 1 hour, after that just consume.