Heat milk to 175 to 185 degrees F and hold it at that temperature for 15-30 minutes.
Allow to cool to 110 degrees F and skim off scalded layer. Pour into a quart sized clean Mason jar.
Stir in 1/4 cup yogurt or starter until well combined.
Put a lid on the jar, wrap the jar in a large towel and place it in the oven with the light on or one of the other culturing methods listed in the notes section below.
Keep warm at 110 degrees F for 6 to 8 hours or until firm.
Remove 1/4-1/2 cup yogurt and set aside (or freeze) for your next batch of yogurt.
Move yogurt to the fridge and store for up to 14 days.
Yogurt Maker – As I mentioned before, I don't own kitchen appliances that don't pull double-duty, so I don't have a yogurt maker.
Instant Pot – If your Instant Pot has a yogurt setting, as mine does, you can use your Instant Pot to culture the yogurt. It will keep your milk at a perfect 110 degrees F. However, I don't like to tie my Instant Pot up for 4-6 hours at a time, so this option doesn't work well for me.
Towels & Ice Chest – I've heard many people use the towel and ice chest method. Simply wrap your jars in large towels, then place them into an ice chest and close the lid. Some people even add jars filled with boiling water to the ice chest to maintain more heat.
Crockpot – In the past, I used to fill my crockpot about halfway with hot water, place my jars of yogurt into the crockpot then turn the knob to “keep warm”. This would work great for me, but you'll want to test your crockpot settings to make sure it's not heating your milk up too much.
Microwave or Oven Light – What I do now is I place my jars, wrapped in towels, into my microwave. If I turn on the overhead light to my stovetop, this heats up the microwave to the perfect “incubating” temperature to culture my yogurt. Some people will wrap their jars in towels and place them in the oven with the light on.