I am asking about voluntary fasting: How is it performed?

Voluntary fasting, like obligatory fasting, requires intention. However, it is not a condition that the intention be made before dawn. Rather, the intention is valid if made before al-zawwal (midday) provided the fasting person has not consumed anything that breaks the fast, as held by the majority of jurists. In voluntary fasting, it is a condition to abstain from things that break the fast from dawn until sunset. If a person observing a voluntary fast wishes to break it, there is no sin upon them, as the Prophet (peace and blessings be upon him) said: "The person observing a voluntary fast is their own master; if they wish, they may fast, and if they wish, they may break their fast." It is, however, recommended for them to make up for it later.