Here is the way I did the yogurt in the crock pot. I really turned out great! The younger two kids really liked it. I do sprinkle a little smidgen of sugar in mine. Adelaide likes a little honey. I put fresh raspberries and blueberries on mine while Adelaide likes fresh strawberries!
I have only made this twice and it has worked great both times!
(I think that the crockpot I use is six quarts.)
1 gallon whole milk
1/2 cup yogurt with fat in it. Don't use fat free! Check also on the label to make sure it has live cultures. I used plain Yoplait once and then a full fat organic one that I got at Trader Joes down here.
You also will need a candy thermometer. I got one at Walmart for like six bucks.
Pour the milk into the crockpot. Cook on low for about five hours until the temperature of the milk reaches 180 Degrees. (Mine takes about 4 1/2 hours. I'm sure crockpots will vary!)
Let milk sit until the temperature reaches 105 degrees. This can take several hours!
Once the temperature reaches 105 put a 2-3 cups of the warm milk in a bowl and whisk in the yogurt. Pour into the crockpot with the rest of the milk and whisk together. Wrap the crockpot in a large bath towel and place in the oven. (You'll need to take out an oven rack!) Leave in the oven overnight. No you don't need to have the oven on. It just keeps it out of drafts.
In the morning you have yogurt! You can save 1/2 cup of this yogurt as a starter for your next batch.