If one has a pan of chicken with liquid in the bottom of the plate, an, is it permissible to take a pan of chicken from the refrigerator and place it on a warming plate on Shabbat morning to heat up for the shabbat day meal?
Please send sources.
Concerning a regular electric warming plate, which can be used for keeping food warm but not for actual cooking, Rav Moshe Feinstein (Iggros Moshe, vol. 4, no. 74, sec. 35) permits placing food directly on the plate, because this is not considered an ordinary method of cooking (based on Shulchan Aruch, OC 253:5).
Many authorities do not mention this leniency (see also Shemiras Shabbos Kehinchasa 1:25), and some do not rely on the heiter, but I heard from Harav Scheinberg zt”l that one may rely on it. A common custom is to place something on top of the hotplate, such as an upside down pan, and place the food on it, and this is recommeanded.
However, this ruling applies specifically to dry food, and not to liquids. If the amount of liquid is not significant, and the chicken is only damp with sauce, it can be heated in the above manner. But if the amount of sauce is significant, it is not permitted to heat it on Shabbos.