"Cory Monteith was a great leader as a character and person in real life," Salling tells PEOPLE of his close friend and costar, who died last summer at the age of 31. "It's a big, obvious hole. I still think about him all the time."
"He was kind of like the quarterback of the show, which sounds cliché because the [tribute] episode was called that, but he was kind of like that in real life," he added.
Now that most of the veteran cast members are reuniting for the final season, Salling says, "It's like we never left."
"I've been through so much with some of these cast members," says the actor. "Traveling the world, international tours … it's really like family."
As for whether the reunion has offered any closure for the lost member of their family, Salling is skeptical: "I don't think there will be any closure. Not yet."
While the actor/singer/multi-instrumentalist is still in production with Glee, he's also looking toward the future.
Along with his friend and collaborator Mike Miller, Salling recently debuted songs for an original musical comedy project, dubbed Camp Coyote. The concept features campy tunes performed by the duo's alter egos, Saw and Mill – who Salling described as "rival male beauty pageant contestants."
Courtesy Mark Salling
Despite six seasons on the emotional rollercoaster that was Glee, Salling says he's still not in any hurry to put it behind him.
"I'm going to miss it. Absolutely.”