It took 10 years but with “The Holdovers,” Paul Giamatti and director Alexander Payne reunite for the first time since the Oscar-winning “Sideways.”

An offbeat buddy comedy set in 1970 at an all-boys Massachusetts boarding school, the title refers to Giamatti’s single, dedicated but universally hated, long-term teacher Paul Hunham who is to supervise the few students that remain at Barton Academy over Christmas vacation.

Thus a life-changing journey begins for Hunham with his troubled, if brilliant, student Angus Tully (Dominic Sessa in his screen debut).

While Payne won his Oscar co-scripting “Sideways,” “Holdovers” lists him only as director.  This project didn’t begin with David Hemingson’s script because, Payne said in a post screening conversation, “There was no script.

“I got the idea for the movie from a fairly obscure 1935 French film called ‘Merlusse’ by the director Marcel Pagnol, who has other masterpieces. That’s maybe one of his more forgotten films. But I saw it at a film festival a dozen years ago and thought, That’s a good premise for a movie. I just held on to it; I didn’t do anything with it.

“I had gone to a private school in Omaha and actually ended up in a boarding school in Massachusetts. Four years ago I got a pilot script, set in a boarding school in Massachusetts, that was very well written. I called the writer and said, ‘I love your script. I don’t want to make it. But would you consider writing a feature set in that very same world?’ And he accepted – that’s how it happened.”

While it wasn’t written specifically for Giamatti, he was the only one considered.  “I’ve been dying to work with that cat again all these years,” Payne said. “This was very much written with him in mind.

“I sent him an early draft, just to check in with him. Because he’s smart, good with material and would have good instincts about it. Like we’re on the right path, both for him specifically and as a movie in general. And he was in.”

As for Angus, Payne’s casting director waded through 800 video submissions – without finding their lead.

“Finally, we activated a plan which was to call the schools where we’re actually going to shoot and say, Whom do you have there?

“And there Dominic was at Deerfield Academy. A senior, a star in the drama department, he’d never been in front of a camera. He wanted to be an actor and was applying to Carnegie Mellon (he got into Carnegie Mellon).

“It was interesting for me to observe that some people have a talent, they’re born to do it.”

“The Holdovers” opens Friday