Cover the pad with a dishtowel and place a ceramic casserole dish on top of it. Meanwhile, heat the milk until it reaches 180°, then turn the burner off.
Allow the yogurt to cool until it reaches 105-109°, or as my mom used to say: "until you can dip your little finger in and can tolerate it to the count of ten."
Ladle approximately one cup of the warm milk into the yogurt and mix until the yogurt is completely diluted.
Pour the diluted yogurt into the warm milk and mix until incorporated. Then carefully pour the milk/yogurt mixture into the warmed casserole dish.
Place the lid on the dish and cover with a towel. Do not disturb for eight hours.
Once it's ready, there will be some whey that rises to the surface. Place a few folded paper towels over the yogurt to soak up the extra liquid.
Notes
Periodically replace the paper towels as they get soaked with whey.
Another option is to drain the whey and use it to make this healthy yogurt drink!