The footstool (not mentioned in Kings) was an essential appendage to an Oriental throne; it appears everywhere in the Egyptian, Assyrian, and Persian sculptures.
Related Commentaries of 2 Chronicles 9:18
2 Chronicles 9:18
18 And there were six steps to the throne, with a footstool of gold, which were fastened to the throne, and staysf on each side of the sitting place, and two lions standing by the stays: