At this point I put the stoneware part of my slow cooker into the Wonder box. This will hold the temperature for long enough for the lactase (milk sugar) in the milk to be eaten by the culture bacteria and ferment the milk into yogurt. The yogurt will need to be in the box for 8-10 hours. If you don’t have a Wonder box, heat your oven to 120° and put the stoneware with the milk in it, into the oven. Turn off the heat and let it sit in the oven for 8-10 hours. Any longer than that and the yogurt will go a step further and make cheese curds. Now cheese curds have their place in the world, but I want yogurt.