Hey mr Papper, sorry but I forgot to respond to your question.
I did a post on the amazing wonderbag a couple of months ago - here is the link if you'd like to check it out. It's basically a fabric bag, insulated with repurposed foam chips, like a slow cooker but no electricity required. The food of course has to initially be brought to boiling point on the stove top and then transferred to the wonderbag; great for working ladies. It was initially designed for rural folk but is used more widely now. I have used it for proving yeast bakes as well and now know thanks to @buckaroo that it's great for making yogurt like @apanamamama does in her instant pot :)