So no need to clean the underneath part?
One can only Kasher(in
English terms.)
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PREPARING THE KITCHEN FOR PESACH
COUNTERTOPS
Ceramic Tile Countertops Cover the countertop with a water-resistant covering such as plastic. (The countertop itself cannot be kashered; therefore, it must be covered.)
Formica or Plastic Countertops There are different opinions as to whether formica or plastic countertops can be kashered for Pesach. Consult your rabbi for guidance.
Granite, Composite Stone (e.g. Quartz) or Stainless Steel It is preferable to kasher a countertop by pouring boiling water in conjunction with an even melubenet (a heated stone).
To kasher with an even melubenet: Attach a stone to a clamp, and heat the stone on the stove for a minute. While pouring the boiling water on the counter, move the stone along on the counter with the boiling water so that the water is reheated on the surface of the counter. The stone may need to be reheated on the stovetop several times, since it can cool down quickly.