Fellow Queensland and Storm great Cameron Smith has flagged his interest in joining Slater's brigade, while former teammate and ex-Maroons star Greg Inglis is understood to be open to returning in a coaching capacity.
Now, Hannay will join Slater and Thurston in making a return to the State of Origin landscape.
Hannay endured a difficult season with the Sharks this year after taking on the temporary role as Cronulla's senior coach following the departure of John Morris in April.
“I spoke to Josh last week - I’m keen to have him on board,” Slater told News Corp.
“Josh was one guy I was keen to chat to and when I called him, Josh was really keen about coming on board and contributing.
“He has an intelligent football mind and he’s a Queenslander. He has pulled on the Maroons jersey as a player, so he will add a whole heap of value to the group.
“Josh did a tremendous job at Cronulla this year, only just missing the finals series, and having to deal with a whole heap of situations."
Hannay will also continue as an assistant with the Sharks next season, working under incoming senior coach Craig Fitzgibbon.
“I’m honoured to be involved in a new coaching group with Billy and the other people he’s going to have on board,” Hannay said on the announcement.
“To be part of that is going to be exciting, but also (we’re) acutely aware of the challenge ahead in getting the shield back against a New South Wales team that looks probably as strong as it has been in a long time.”