Is it permissible to pave the grave with cement and cover the deceased with it, knowing that cement has been touched by fire? And what is the prescribed method for burying the dead?

If the intent behind furnishing the grave with cement is to construct its interior with it, then this should not be done, as the Sunnah is to bury the deceased directly in the earth without a covering, and the grave should be covered with unbaked bricks (labin) or anything untouched by fire. However, if the intent is to plaster and tile the grave, this is also impermissible, and the scholars have explicitly stated its detestability.