The ideal size of the holes in a hookah foil will depend on the type of charcoal you are using, the amount you are using, and your personal preference for the amount of smoke you want to inhale. Typically, the holes should be small enough that the charcoal does not fall through, but large enough to allow enough air to flow through to keep the coal burning. A needle or toothpick can be used to make the holes, but be careful not to make them too large or too close together.
Can I leave holes empty or should the charcoal cover all the holes?
As for the charcoal placement, it’s recommended to cover all the holes with charcoal. This allows for the smoke to be drawn through the hookah bowl and into the water, providing a cooler and more flavorful smoke. However, you can try different configurations and see what works best for you.