Homemade Slow Cooker Yogurt

1 gallon milk
1 cup plain yogurt with active cultures

Pour the milk into a slow cooker on low setting for about 3 hours. You want the milk to get 180 degrees. (If you want your yogurt ready to strain at about 8 o'clock in the morning, begin this process about 2-4 o'clock in the afternoon the day before.)
Unplug the slow cooker and let it sit for 3 hours. (It should be about 5-7 o'clock when you start this phase.)
Add to the milk the cup of yogurt. (It should now be between 8-10 o'clock.)
Wrap the Crock-Pot with a towel and let it sit unplugged for 8-12 hours. (It should be about 8 o'clock in the morning when this phase is complete.)
Strain off the whey by lining a collander with cheesecloth and then putting the collander in a larger bowl.
Pour the yogurt into the collander with cheesecloth and let the whey drain into the bowl.
You can save the whey to use as a healthy water replacement in recipes or discard it.
You and add fruit compote or honey to the plain yogurt, as desired.

Source: Large Family Table