Hello, Is one required to treat a hot plate, ie a platta, as a blech, in that one needs to put the food (precooked solids of course) on top of another kli and not directly on the heating element? I heard that since people do not usually use a plata for cooking it is not considered marit ayin and that there is no problem with putting food directly on the plata.

This is an argument amongst the Poskim. Most of the Poskim hold that a Platta is regarded as a covered flame, and therefore precooked solids can be placed on Shabbat on the Platta on top of a plate, pot cover ect. Precooked liquids cannot be heated on Shabbat. Rabbi Yitzchak Grinblat