After Shabbos allow to cool, drain the water, allow to dry.

There are many different thoughts and traditions associated with food warming on Shabbos.

Some people do not rewarm any food that have removed from standard blech and have been allowed to cool down, regardless of the fact that the food is full cooked and dry.

If you follow this more stringent halachic principle you can use the K'deirah Blech as a safety valve to avoid inadvertently cooking on Shabbos. For example, if you accidentally remove a pot from the blech to serve dinner, there is no question about replacing the pot onto the K'deirah Blech, although , it would not be permitted to do so with a standard blech.

Others freely remove and replace dry foods onto a standard blech, often without regard to the principle of YAD SOLEDET BO. For them, the K'deirah Blech is the only useable blech. It permits foods to be heated HOT, not just warm in a way that is well within the boundary of accepted halachic principles.

Still others rewarm food using a standard blech but are careful to avoid the temperature limit set by YAD SOLEDET BO. at best they can expect a room temperature meal. With the K'deirah Blech there is not limitation of YAD SOLEDETS BO. The fear of bishul is reduced with the K'deirah Blech.

HOW IS THE K'deirah Blech MORE EFFECTIVE THAT A STANDARD BLECH?

A good blech that is hot to the touch at all of its corners is actually a bad blech for use on Shabbos since cooled foods may not be returned to it on Shabbos.
A poor blech that is cool to the touch at corners is useable but your food stays cold. Therefore, if you are careful about following Halacha, you must pay good money for a blech to eat a cold meal. The other choice is to pay good money for a good blech and eat a cold meal since the blech is not useable on Shabbos.

Does this mean that only chulent of other foods that are left on a standard blech since before Shabbos are permitted to eaten?

Happily, the answer is NO!!!!
Foods may be reheated on Shabbos if proper techniques and precaution are used.

INTRODUCING THE K'deirah UN-Blech

Although it is called a blech it is actually not a blech, it is The UN-BLECH
The K'deirah UN-Blech is an engineered solution to Shabbos food warming problems.

The lower tray of the K'deirah Blech contains hot water and is therefore a K'deirah. This means that the food to be warmed can be placed anywhere on the K'deirah Blech regardless of the temperature. Yad Soledet Bo does not apply when the principle of K'DEIRAH is applicable.

More user info K'deirah blech