FOR TWO decades at the New Yorker, editor Bob Mankoff famously had a weekly open call, at which cartoonists would submit their works for face-to-face office encounters that, more often than not, ended in swift rejection. Now, however, as he heads to Esquire magazine, Mankoff is scrapping that entire model.

“That selection process,” Mankoff tells The Post’s Comic Riffs, “is delusional.”

That’s right — as much as he relied on this gags-in-hand approach, the veteran editor is convinced that it wasn’t the best system for consistently developing the best humor. Each line drawing effectively only got an instant audition, so even promising gags that didn’t quite “sing” right then and there were quickly shown the stage door.

Enter a new stage of collaboration.

“I want to try something new,” Mankoff says. “I’ve had this idea for a long time, but in the New Yorker context, it didn’t make sense.” As he takes the reins this week as the humor and cartoon editor at Esquire, he envisions a way to try to foster stronger comedy — an approach that just might “reinvigorate the ecosystem of magazine cartoons.”

The idea: What if he were to work closely with a handful of different cartoonists every issue, in a process that he says would “feel less hierarchical” and “more productive”?

“It’s important to use these editorial muscles that I’ve developed over all these years,” says Mankoff. His goal is to spotlight each humorist’s voice by helping to develop their material.

As such, Mankoff wouldn’t just work with artists, but also performers. “I want stand-up comedians to work with cartoonists, too, to [explore] what a stand-up sensibility could be in a magazine.”

That collaborative approach, he notes, is more like what the New Yorker was still doing a half-century ago, when illustrators and gag writers might be paired on a cartoon. And given today’s technology, you can collaborate in “a virtual writers’ room” — one in which a stand-up like Pete Holmes, he says, might work with cartoonists like Alex Gregory and Matthew Diffee, who grew in prominence within the pages of the New Yorker.

“Combining different skill sets could be very powerful in … heightening the quality of humor,” Mankoff says. “That’s my ambition through collaboration, and that’s [new Esquire Editor in Chief] Jay Fielden’s ambition, too. I’ve known him since 1997. We go back a long way, and we have a great working relationship.”

(Mankoff notes that he illustrated his move from the New Yorker to Esquire this week by literally rendering a stock desert-isle setting, a visual signal that he hopes to move away from cartoon tropes.)

“I look forward to working with new talent, too. It will be a commission process, essentially, like working together on an article,” Mankoff says. “We will all have skin in the game, writers can be emboldened — and my door is open.”