The Saponification Process

Saponification is the hydrolysis of an ester under basic conditions. The direct products are a carboxylic acid salt (That is the soap) and an alcohol (Glycerol).

Source: https://chem.libretexts.org/

That is why we use Sodium Hydroxide(NaOH) and Water in all Soap Making Formulas together with an oil as oils/fats are composed of esters.

In the soap products' page, you can find which type of oils were used as well as  other optional ingredients used besides the must have NaOH and H20.