Actress and model Suki Waterhouse and entrepreneur Poppy Jamie were lying in bed about a year and a half ago when the idea came to them. It had been a long week: Waterhouse had spent gruelingly hot days shooting a film in the deserts outside Los Angeles, and the two women had passed the weekend recuperating by wandering Los Angeles’s Bustown Modern boutique when they happened upon a fabulous vintage fanny pack — “the coolest bag ever,” as Jamie remembered it.

“We were like, ‘Why don’t people make bags like this anymore?’” she said, wondering. And then: “Wouldn’t it be cool if we…”

And thus the seeds of Pop & Suki were sown. Though Jamie and Waterhouse have been friends for nearly four years, they’d never before undertaken a creative collaboration; over the past 18 months, they conceived, developed (in collaboration with a design team), and executed the new, customizable accessories line bearing their names.

Waterhouse wears a Burberry sweatshirt, $795, burberry.com; Pop & Suki charm, $55, popandsuki.com; Pop & Suki chain necklace, $150, popandsuki.com; her own earrings and rings.

GIF by JJ Ren. Styled by Caroline Grosso. Produced by Biel Parklee.

“It’s a dream, being able to call your best friend and gossip about the night before and then have a work call for an hour,” Jamie said, speaking over the phone from Los Angeles. It was Halloween, a frigid day where I sat in New York but balmy and sunny where the two friends were just wrapping up a photo shoot. “We’re kind of soaking up the rays,” Jamie said. “Storing away some sunshine.”

It was also, perhaps more significantly for Waterhouse and Jamie, the day their pre-orders finally shipped and the day before the official collection launch.

“It’s a surreal moment seeing them all packaged up and ready to go,” Waterhouse said. “It’s like our giving-birth day.”

Pop & Suki opened for pre-orders in mid-September; since then, pieces from the collection have been spotted on the likes of Lena Dunham, Amber Valletta and Lucy Hale.

For their first venture, Waterhouse and Jamie designed two silhouettes (a small leather camera bag and larger suede shopping tote) in three distinct colors — black, a dark reddish cognac, and pastel pink — with personalized options like monogramming, charms, tassels, and, for the camera bag, a selection of six different straps. (Including a waist strap — their imagining of a fanny pack bringing the Pop & Suki origin myth full circle.) The bags are versatile, convertible day-to-night pieces, with hints of the retro, vintage aesthetic that first inspired Waterhouse and Jamie’s venture. The pieces synthesize their respective aesthetics: for Jamie, it’s girlier, more polished; for Waterhouse, more tomboyish, “sloppy,” she joked.

From left: Waterhouse wears a Burberry sweatshirt, $795, burberry.com; F.R.S For Restless Sleepers trousers, $503, net-a-porter.com; Pop & Suki charm, $55, popandsuki.com; Pop & Suki chain necklace, $150, popandsuki.com; Pop & Suki bag, $195, popandsuki.com; Pop & Suki wide bag strap, $35, popandsuki.com; her own earrings and rings. Jamie wears a Marni dress, $1,870, net-a-porter.com; Carven sweater, $380, Forty Five Ten, Dallas, 214.559.4510; Pop & Suki chain necklace, $150, popandsuki.com; Pop & Suki bag, $195, popandsuki.com; Pop & Suki fanny strap, $25, popandsuki.com.

GIF by JJ Ren. Styled by Caroline Grosso. Produced by Biel Parklee.

The brand’s Instagram is a treasure trove of cotton candy-colored found images, Pantone chips, and shots of friends and fans modeling Pop & Suki designs. (“I dream a bit of looking like a fairy or ice cream,” Waterhouse said. “I think it stems from an early love of Power Puff.”) Fittingly, one of the duo’s customizable options is a black heart split down the middle reading “Best Friends” in white lettering, a more sophisticated take on friendship necklaces exchanged at summer camp and in first grade classrooms.

But, as Waterhouse tells it, the collection less emphasizes best friends and more celebrates women with a strong point of view and sense of purpose — much like Waterhouse and Jamie themselves. “Me and Pops were always just super in awe of girls, really,” she said, citing artist-activists like Rowan Blanchard and Dunham, entrepreneurs like Sheryl Sandberg and Arianna Huffington, and actors like Emma Stone and Sasha Lane.

“We’re real lovers of women.” Jamie jumped in, noting that not too long ago, they might have faced even greater challenges in funding and executing their vision. “We don’t take it for granted,” she said. “The environment has changed to enable us to be entrepreneurs.” Pop & Suki emphasizes sustainability, both in materials and production; the accessories are manufactured in Los Angeles, and the direct-to-consumer model ensures a more affordable price point. (It’s an analogue, in many ways, to a fledgling Everlane.)

Jamie wears a Stella McCartney dress, $995, tank top, $1,195, and trousers, $860, stellamccartney.com; Pop & Suki bag, $195, popandsuki.com.

GIF by JJ Ren. Styled by Caroline Grosso. Produced by Biel Parklee.

Though they’ve only just launched, Waterhouse and Jamie have already started imagining the next Pop & Suki collection. They began the design process with hundreds of ideas that they had to whittle down to a focused, core collection: “We really created the bags that we wanted to have and the bags that we couldn’t find,” Jamie said. But there are new bags to dream up — maybe a satchel or a backpack.

“We love making fashion individual,” Jamie said. “That’s what we really wanted to allow.”