No one is going to put  coals straight onto the tobacco, unless you are smoking  the very strong, unflavoured Iranian tobacco.
Some people put on a wire mesh instead of using aluminum, but it doesn’t¬† keep the coals as hot, and the heat inside the tobacco bowl well. For that aluminum¬† foil is the best¬† bet.
I’ve tried the very thick aluminum foil , but it burns the tobacco too much and of course re-using it is impossible, since with any foil, the¬† protective layer burns after one time any ways.
Best is to buy the ready cut in a circle thin foil and make sure that you put the shiny part down toward the coals  underneath so that it reflects the heat down toward the coals instead of taking the heat energy and lifting it away from your tobacco.
Hookah 1