When the start-up ad agency Griffin Archer opened its Warehouse District doors 18 months ago, it had two clients and three employees.

Today it is debt-free, making money and double in size — all the way up to six employees.

Successful? So far, yes.

“We do our best work when we have a direct relationship with our client,” founder and CEO Ellie Anderson said of the strategy to keep Griffin Archer small in comparison to bigger legacy agencies. “I love to do new business and be client facing.”

But Griffin Archer is also a textbook example of the new generation of ad agencies in the Twin ­Cities that have an office for their principals but farm out work on a client-by-client basis to freelancers to keep overhead down.

“It’s easy for us to pick and choose who is best for an assignment,” said Kelly Thompson, Griffin Archer’s president and director of brand strategy. “Larger agencies are so much more about ­process, and the further you move up the management chain, the more removed you are from the [advertising] craft. Our management team here is very hands-on.”

Thompson and Anderson personally work with each of the agency’s clients, which range from the Denver Museum of Nature & Science to upscale Arta Tequila.

“Both of us work with every client so no one is left high and dry if someone is on vacation,” Thompson said.

Veteran ad agency executive Steven Wehrenberg, who now teaches advertising at the University of Minnesota, likens the new agency model to that of a Hollywood production company that sees a screenplay it likes and then outsources the creative talent.

“The advantage is you don’t have all that overhead. You don’t have to employ all of these people and feed the beast with projects you might not want. You can get the right talent for the right project,” Wehrenberg said. “We’re very picky,” said Thompson. “We date before we hire.”

The advertising DNA of Thompson and agency founder Anderson is considerable.

Before starting Griffin Archer — which is the first and middle name of Anderson’s 3-year-old son — Anderson, 39, spent 10 years at the Minneapolis agency Carmichael Lynch where clients included Porsche, Harley Davidson and Subaru. For Subaru, Anderson helped start the auto manufacturer’s signature “dog tested, dog approved” advertising campaign using her own dog in some of the TV spots.

Thompson, 40, also came from Carmichael Lynch. Before that, she was at the Minneapolis agencies Space 150 and Campbell Mithun. Her ­client experience includes Burger King, General Mills, Jack Link’s and Rubbermaid.

Griffin Archer’s third opening-day employee, Glen Wachowiak, had Carmichael Lynch experience in his blood, as well, working on campaigns there for Gibson Guitars, as well as Harley and Porsche.

Griffin Archer’s first client was the Denver Museum of Nature & Science, which Anderson brought with her from her days at Carmichael Lynch.

“What Ellie brings to the table is a balance between thoughtfulness for the audience and a compelling approach,” said Amanda Bennett, the museum’s director of marketing.

The museum’s most recent large exhibit handled by Griffin Archer is called “Traveling the Silk Road” and is about the ancient trade route from China to the Roman Empire.

“The real bonus is Ellie knows my business as well as I do,” said Bennett. “She’ll have a conversation with the curator of an exhibit and then pull in the right art director to get the element she wants. Not every person on every agency can get into the mind-set of Genghis Khan or a pirate.”

Griffin Archer’s other clients include Element Electronics, a U.S.-based manufacturer of flat-screen TVs, Minnesota-based Luminara, which makes and sells increasingly popular artificial candles, Learning Rx, a Colorado-based education company, and the International Exhibition of Sherlock Holmes.

One of Griffin Archer’s next projects is a traveling show of Beatles memorabilia called “The Magical History Tour.” Earlier this summer, the agency landed Sotea — the maker of carbonated tea products — as a client. Griffin Archer’s assignment is to help the Wisconsin-based company rebrand itself on a national stage.

“We approach each client so differently. It is truly a creative endeavor, working together to create something unique for their brand and category,” said Anderson. “We’re doing very well.”

Wehrenberg said the trend in ad agency ­compensation is away from flat fees to a pay-for-performance formula.

“Most talented people will always find work and make money,” he said. “And in this case, you have two dynamic women in a creative market that’s been all guys for a couple of generations.”