You can use an old crock pot on low with the jars sitting in water and the lid off but the new ones get too hot.
You can also use an Insta-pot.
The longer you let it culture the more sour it will be. Five to six works best for me. Twelve is way too sour and four is just bland.
If you are going to use store bought yogurt for culture use plain and either Fage for Greek or Skyr for Icelandic.
Or you can just buy the cultures.
You will need to drain the yogurt. Because I like to make the thick stuff I put a couple of layers of cheese cloth in a strainer and set it over a bowl and put it in the basement fridge for about 24 hours.
Thanks for the tips! I’m leaning toward the really THICK stuff. Yum! :)