The Chamber of Petitioners was a room in the Tower of Commerce on Ferenginar.
Here, the Grand Nagus received Ferengi petitioners asking for business advice, sitting on a throne. Zek received petitioners, including Leck, here in 2373 and temporarily made Quark his First Clerk, who briefed the Nagus on the petitioners. (DS9: "Ferengi Love Songs")
The name "Chamber of Petitioners" was not mentioned and is derived from the script. In "Profit and Lace", the Nagus is instead implied to operate out of the Chamber of Opportunity.