Rashi on II Kings
At his place. The place where the king stands in the Beis Hamikdosh.1See above 11:14. It was a special place in the Beis Hamikdosh where the king would stand when addressing the people.
Ralbag on II Kings
And the king stood on the platform: It would seem that they build a platform there, and the King would stand on it at the time when they read the Torah, as was mentioned with regard to the communal Torah reading.