Walt Frazier likes bold fashion and flashy suits. But he knows the only way to win in the NBA is with lunch-pail defense.

After a Knicks spending spree that netted seven free agents, none of them an All-Star, Frazier says the only way the club will be relevant is if the defense is up to snuff. And he thinks the Knicks’ roster can pull that off.

At a PUMA event Monday night at which a new “Clyde”-inspired sneaker was unveiled, the Knicks legend told The Post he hopes coach David Fizdale employs a frenetic, full-court pressing defense to take advantage of their depth. Frazier said Fizdale should use the model of Al Attles’ 1970s Golden State teams.

“The key to winning is always defense to me,” said Frazier, who played on the Knicks’ only two championship teams in 1970 and 1973 and is their longtime MSG Network broadcaster. “I wear this [championship] ring with a lot of pride. I think they have a lot of good defensive players they signed. If they come out with that tenacity, the Garden crowd will come out to support them.

“They realize they’re not an elite team, but if they give 100 percent, they’ll get the support of the Garden. With very aggressive defense, they can make the playoffs.”

The Knicks haven’t made the playoffs for six straight seasons, and most prognosticators believe the drought will extend to seven despite the signings of Julius Randle, Marcus Morris, Bobby Portis, Taj Gibson, Elfrid Payton, Wayne Ellington and Reggie Bullock. Neither president Steve Mills nor GM Scott Perry has faced the media since a post-draft press conference on June 21. Training camp begins Sept. 30.

“I was disappointed we didn’t get a star,” Frazier said. “But I like Plan B. There’s a lot of talent there with versatility.”

Frazier invoked the New York market in giving his reason why some stars don’t want to sign with the Knicks.

“The ferocity of fans,” Frazier said. “It’s a professional fishbowl, you can’t get away from it. Everyone wants to know how you’re doing, why you’re doing it, why you aren’t doing it. That’s why a lot of players now don’t want to play in New York because of the scrutiny. You can get the same money in Indiana and some other places without all the criticisms you get in New York. New York is not for everybody, but that’s the pressure I like.”

Frazier, who was awarded the first NBA sneaker contract more than 40 years ago by PUMA, was joined on stage Monday by new sneaker partners Kevin Knox and RJ Barrett, the Knicks’ last two lottery picks.

The addition of the veteran free agents, Frazier believes, may result in Knox and Barrett coming off the bench this season.

“It will put pressure on these young guys,” Frazier said. “You can’t take it for granted as high draft choices, they are going to start.”

In lauding the two lottery picks for their strong character, Frazier noted Knox and Barrett both have strong father figures in their lives. Knox’s father, Kevin Sr., won an NCAA title in football at Florida State and was drafted by the Bills. Barrett’s father, Rowan, starred at St. John’s and played overseas basketball.

Frazier wants to build a strong relationship with Knox and Barrett and take them shopping for suits this season. Frazier retold his fashion process: He frequents fabric stores to get ideas for his tailor to turn into suits for the new season. Barrett wore a pink suit on Draft Night, but said Frazier’s wardrobe is too colorful for his taste.

“It takes confidence,” Barrett cracked. “I’ll be honest: I’m just not that confident.”

When Frazier was asked about his career highlight, he went back to Game 7 of the 1970 Finals. Willis Reed, after taking a painkilling shot for his ailing knee, became a folk hero for sparking the Knicks by hobbling out of the tunnel. But Frazier notched 36 points, 19 assists and 7 rebounds to clinch the title.

“They call it the Willis Reed game,” Frazier said. “I call it bulls–t. I did everything, including sell hot dogs at halftime.”