Skinny ties and slim-cut suits á la Don Draper. Bell bottoms, tie-dye, and mutton chops á la Joe Cocker. It would be hard to find a period more stylistically dissonant than the late 1960s—which is part of what makes the era so fascinating.

The last throes of the buttoned-up 1950s were fading, while the free-love, anything-goes Age of Aquarius was on the rise. And that explosion of culture serves as the backdrop for Quentin Tarantino’s Once Upon a Time…In Hollywood, one of this year’s most anticipated films.

While the press around film has produced no shortage of great red carpet style, we wanted to know more about the eye-popping, circa-1969 looks from the movie itself: a mix of Mad Men-esque tailoring, badass Steve McQueen-style Hollywood casual, and, of course, the full-on hippie psychedelia. Luckily for us, we got a chance to chat with Once Upon a Time… star (and future Elvis) Austin Butler and costume designer Arianne Phillips at a special dinner put on by Levi’s at the Levi’s Haus in Hollywood prior to the film’s release.

Organized by Levi’s and Phillips, the night brought together Once Upon a Time… stars Butler and Margot Robbie as they hosted cast, crew, and friends for a dinner to celebrate the movie, and to raise awareness for two important charities: Phillips’s Red Carpet Advocacy (RAD), which fosters relationships between talent and their charities to facilitate advocacy via the red carpet, and Margot Robbie’s Youngcare, a non-profit that serves young people with high care needs in Australia. Tucked away in a quiet corner of the Levi’s Haus, we talked ‘60s style, cowboy boots, and what made 1969 such a pivotal year.

Esquire: Quentin Tarantino has one of the most recognizable styles in cinema. What was it like to work with him?

Arianne Phillips: It’s unique. There’s no director like Quentin Tarantino. He’s been on my bucket list, and I really just lucked out. It was an experience that will never be duplicated, unless I get the chance to work with him on his last movie.

Were you fans of late-‘60s style before the film?

Austin Butler: I actually have a mood board that is ever-evolving on my wall in my office. Most of the images are Steve McQueen in the late ‘60s . Like the one with that denim shirt open. Or Paul Newman, just playing ping-pong.

Arianne Phillips: That [St. Christopher] medallion that he [McQueen] wore, that’s actually why I had Leo wear a medallion in the film.

Any favorite elements of ‘60s style?

Arianne Phillips: I think my favorite elements about 1969 style is the fact that, like 2019, it’s a time of change. You can see there are all these microcosms of the world. So I really related to that. And also, what we wear is our identity and how we want the world to perceive us. So I always find it interesting to see the choices that people make. I’m endlessly fascinated by it. And I think 1969, it was the beginning of “anything goes.” Before, like the ‘50s, people looked more the same. But ‘69 is really challenging because it’s a changing time for costumes and also in our story. And I feel like it’s just the same now. And just like then, now you can create what tribe you belong in.

What are some of the challenges of costuming a period film?

Arianne Phillips: I would say the only real challenges were on the logistic side, with so many locations and such a large cast, as well as hundreds of background actors. Luckily for me, I work with a great team and was able to hire some of the best in the business to work alongside me.

Along with Levi’s, what period-specific brands did you use?

Arianne Phillips: We did have some fabulous sunglasses for Margot [Robbie] from Ray-Ban. And also Oliver Goldsmith. Both of which recreated 1960s styles for us.

Any favorite looks?

Austin Butler: I particularly loved wearing a cowboy hat and cowboy boots. Riding a horse and bell bottoms. And the Spahn Ranch T-shirt. That’s still one of my dreams to have that shirt.

Arianne Phillips: I can get you one.

Austin Butler: You have one?

Austin Butler: I think I do. And you had that stampede strap, for horse riding.

Was there anything that made its way into your personal style?

Austin Butler: Honestly, the boots I’m wearing now were in the film. My grandfather was a cowboy, and he wears cowboy boots everyday. But I don’t feel I ever had owned that, in a way. And then with this, I got these before our first fitting. I wore them to the audition.

Arianne Phillips: Yeah, you wore them in there with mud all over them, and I was just like, “You’ve got to wear those.”

Were costumes mainly sourced from vintage clothes or created from scratch?

Arianne Phillips: We made most of the principle costumes, and also sourced from costume houses like Western Costume and Palace Costume, both incredible warehouses with archives of movie costumes. I also sourced from flea markets, vintage sales, and was able to solicit the expertise of vintage archivists and shop owners.

What was the main inspiration for you for the costumes in the film?

Arianne Phillips: The script. One hundred percent. And a long list of references that Quentin gave me to watch. The script was amazing. It was not like anything I’d read. It was like a novel. Just layered with rich characters.