Dear Rabbi. why do later poskim require double wrapping in a clean non kosher oven, when the shulchan aruch, rama, and commentaries on the shulchan aruch up to and inclusive of, the Badei Hashulchan, we do not find such a requirement? All it requires is a "kisui", and nothing else?

Thank you for your question, There is no requirement to double wrap. However, one must make sure that the food is completely covered from all sides. Therefore, there is logic in double wrapping since there might be a whole in the first wrapping. All the best!