Keith Smart and Knicks point guard Dennis Smith Jr. have been summer shooting pals for six weeks, in three cities, for countless hours. And it started in a chair.

The Knicks assistant coach warned Smith the process would be “tedious.” It’s been all of that — and the alliance may turn so successful, the shape of the Knicks’ season could change.

Smart is the former Indiana shooting guard best known for hitting the biggest baseline dagger in Syracuse history. Smart authored “The Shot’’ that slayed the Orangemen for the 1987 NCAA championship.

After the 2018-19 season, coach David Fizdale handed Smart his summer assignment: Make Smith’s jump shot dangerous.

In his two seasons, Smith, the No. 9 pick in the draft for Dallas, posted a mediocre .407 shooting percentage — .316 from 3. Smart said his goal was to get Smith “balance on his jump shot.”

Smith was the key piece in the Kristaps Porzingis blockbuster in late January. Smart noticed quirks from the day Smith arrived in Tarrytown.

“When we traded for Dennis, you have a look at every player how can we help them get better shooting the basketball or passing,” Smart told The Post in a phone interview. “We got together in the gym in February to get a feel, look at his shot, what I can help him with. I got a picture of it.”

In May, Smart flew to Smith’s hometown, Fayetteville, NC, to launch “Project Dennis.” They’ve also worked in New York and Las Vegas during the summer league in early July. They will resume in August.

“It’s getting his delivery system into the shot where he can get more confident shooting,’’ Smart said. “He’s been a willing participant. I told him it would be a tedious process to start. But if we do it all right, he’ll start feeling it.”

In Vegas, Smith was genuinely enthused, saying “a big difference” had already taken place. He projected he would “take my game to the next level and it’s going to put us in the playoffs.”

That’s a lot of pressure on Smart, a former Warriors assistant and head coach who also worked with Fizdale in Miami and Memphis. Smart has always been “The Shot Doctor’’ and is nicknamed “Smarty.’’ He was smart enough not to touch Stephen Curry’s pure launch during their two seasons together with Golden State (2009-11).

Smart said he’s been lucky to always have coaches obsessed with shooting fundamentals — middle school, high school, then with junior college Hall-of-Famer Jim Carey at Garden City (Kan.) Community College and Bobby Knight at Indiana. Taking shots off the side of a wall were commonplace drills.

Five years ago, Smart took up golfing and marveled at how pros deconstructed a swing to its finest component.

“So I wanted to use that approach in basketball shooting because those guys do a great job — how they teach it,’’ Smart said.

Smart went back to the basics with Smith.

“We started shooting in a chair, taking out all the floor movement and just looking at the shoulders,” Smart said. “The delivery of the hands through the basketball. We worked on that for about a week.”

A week?

“I told him it was going to get boring,’’ Smart said. “But don’t get bored with any of it.’’

Eventually, Smith, arguably the 2017 draft’s most athletic player, emerged from the chair and more fine-tuning took place.

“In my day, I was a leaper, I can jump and get off the floor for a jump shot,’’ Smart said. “But I wasn’t in the same position leaving the floor. And so he was in the same boat I was in, figuring out you don’t have to leap off the floor as high as you can. Doing that takes you off balance.

“We tried to slow things down for him, leaving the floor. You see all the great shooters, they don’t leave the floor that high to get their shots off. They just have good lift on their shots. And your feet shouldn’t be off balance when you shoot the ball.”

Smart can’t count the number of Smith summer jumpers he’s witnessed.

“I don’t believe in putting a number,’’ Smart said. “I said, ‘Shoot it until you feel 100 percent comfortable.’ That may be five shots. It obviously went longer. But I wanted him to feel comfortable. It had to be about him. It maybe didn’t feel comfortable until 100 and we went to the next drill.’’

As a point guard, Smith is asked to create jumpers off the dribble, as opposed to spot-up shooters. Smart said finding “better balance’’ on such plays became another major area of emphasis.

Smart would not go as far as projecting Smith’s shooting numbers this season. But the 54-year-old assistant coach said he feels terrific about what they’ve accomplished as the Sept. 30 start of training camp approaches.

“We did it slowly,’’ Smart said. “But the big thing is he had to get the confidence to believe in it. And as we did it, he got more confidence in his shooting. Before you knew it, we were right on track. The only piece missing is live competition when he gets into a real game and puts it all together.’’