What is Salat al-Ayat, how is it performed, and what is the evidence for its legitimacy from the actions of Ibn Abbas?

Prayer is legislated for the two signs of the solar and lunar eclipses by consensus. However, prayer for other signs, such as earthquakes and strong winds, is a matter of dispute among scholars:

Hanafis: It is recommended to pray for every frightful event, such as strong winds, earthquakes, darkness, and continuous rain. Hanbalis: Prayer is performed only for continuous earthquakes, similar to the eclipse prayer. It is also said that prayer is performed for every sign. Shafi'is: Congregational prayer is not performed for anything other than the two eclipses. It is recommended for a Muslim to pray at home and supplicate to Allah upon seeing these signs. Malikis: No prayer is performed for these signs whatsoever.

The most preponderant opinion is that there is no specific prayer for these signs. However, praying and supplicating to Allah at home for the removal of harm is good.

As for the manner of this prayer according to those who permit it: two rak'ahs, with each rak'ah having three bowings (rukūʿāt), three recitations (qirāʾāt), three standings (qiyāmāt), and two prostrations (sajdatān).