In conclusion:
Many people have the practice to turn a pan upside down and place cold fully cooked solid food from the refrigerator on top of the upside down pan on Shabbos morning?
Is this permitted according to the פרי מגדים ?
Learn שמירת שבת כהלכתו פרק א סעיף מד & הערה קכו
And see קובץ הלכות שבת ח”ב פרק כו סע’ לד & הערה מח
Next Question:
If one placed a pan of food on top of soup pot which is on the blech. May one move the pan on Shabbos and place it directly on the blech?
Point to consider
What is the status of a pot of food that is resting on top of another pot which is on the stovetop.
Is it considered on the fire which is גרוף וקטום or is it considered just סמוך לכירה ?
Bring a proof
Review מגן אברהם ס’ רנ”ג ס”ק לג
https://hebrewbooks.org/pdfpager.aspx?req=14325&st=&pgnum=27
Learn שמירת שבת כהלכתו פרק א סעיף מד & הערה קכו
And see קובץ הלכות שבת ח”ב פרק כו סע’ מ & הערה נה
May one move a pot which is placed in the blech in area not directly over the fire to the part of the blech directly over the fire?
Is the entire blech considered a stovetop which
is גרוף וקטום or is it considered just סמוך לכירה ?
Bring a proof
Learn אורחת שבת ח”א פרק ב סע’ סט & ע with the footnotes