Got my wonderbag today which is a thermal cooker .I do use my pressure cooker pots nearly every day so saving energy there .But looking forward in trying this tomorrow will be using my cast iron pot you need to bring food up to a rolling boil for 20 mins you then put the pot with lid on and put it in the bag and it will finishing cooking in there it will take longer then a slow cooker .
Sounds like a modern take on the Haybox they used to use during the war.
Looking forward with interest to your makes!