Sousvide on Shabbat?

I heard of the sousvide cooking method where a device is placed in a pot of water that keeps the water at a constant temperature so the food does not get overcooked.
Since often on shabbat on the hotplate the food gets very over cooked even if it is placed there on Saturday morning for the lunch, I was wondering if the sousvide method can be done during shabbat or how it could be done. Can the pot of hot water with the device be prepared ahead of shabbat and left on the hot plate and then the food in sous vide sealed plastic bags could be placed in the pot of water on Saturday morning?

Putting food in a sous vide bath on Shabbat would be prohibited.
To heat food on Shabbat in a permissible manner, one must fulfill a few requirements. The food must be a solid dry food with no liquid in it and it must be fully cooked. In addition, one may not heat food upon an open fire. One must cover the fire with a piece of metal to show that this is not cooking. Even once the fire is covered, if the food is in an area where it will reach yad soledet bo (about 115 degrees Fahrenheit) it is considered as if it is on an open fire and one may not place the food there. There are some exceptions to the rule of food reaching higher temperatures, such as placing food on a heat source that is never used to cook like a radiator or urn.
A sous vide is a device that is used for cooking. Therefore, one would not be able to use it to reheat food on shabbos without covering the heating element, something which is impractical.
There is an additional issue with using a sous vide to heat food. The food being heated is placed in a bag inside the water, and the hot water completely encompasses the food. This violates the prohibition of hatmana, insulating food on Shabbat with something that increases the food’s temperature.
Due to the above reasons one should not use a sous vide to heat food on Shabbat.
All the best
Rabbi Shay Tahan