These slices of pork play a supportive role for the ingredients when turning it over and after it's turned over they are at the lowest position, preventing the ingredients from burning and enhancing the flavor because fat permeates all the ingredients.
こうすることでひっくり返す時に具の押さえとなり、またひっくり返した後一番下に来ることで、材料が焦げ付くことを防ぎつつ、具全体に油が回り香ばしさが増す。