When an accomplishment onscreen seems effortless, it reflects true mastery of a craft. For five costume designers of potential Oscar contenders, the weight of their undertaking — wrestling with ensemble casts and specific periods — remains undetectable on the screen.

Donna Berwick’s work on director Spike Lee’s “Da 5 Bloods,” about four Vietnam veterans returning to the country, meant designing for a cast in the present day as well as the 1960s.

With only about a week of prep time in Los Angeles before flying to Thailand for filming, Berwick was provided with customary initial measurements and sizing for the cast ahead of any fittings. The information turned out to be completely outdated for multiple actors. When they tried on their custom-sewn military uniforms, “the pants were too small,” says Berwick. “We had to cut them open and add pieces.”

During the present-day scenes, a distinctive pop of color comes from an instantly recognizable MAGA hat that evokes considerable emotion “without anyone saying a word,” says Berwick, noting that the accessory was one on which “Spike [Lee, the director] insisted [and star] Delroy Lindo resisted.”

As with the MAGA hat, individual pieces can help define a character. Berwick says her research revealed many “of the African-American soldiers then wore a lot of African paraphernalia and Black power symbols.” So she bought beads to handcraft a necklace for Stormin’ Norman, played by Chadwick Boseman in one of his final film roles. Boseman liked it so much that he asked to keep it; Berwick agreed.

Sandy Powell also worked with a special necklace on director Julie Taymor’s film “The Glorias,” which was based on activist-writer Gloria Steinem’s novel “My Life on the Road.” Steinem, who also appears in the film, loaned Powell a necklace from her personal collection. It was one that Native American activist Wilma Mankiller had given Steinem, says Powell of the memorable piece that Julianne Moore wore in her portrayal of Steinem. Real-life politician Bella Abzug, portrayed by Bette Midler, also had a distinct style that had to be incorporated into the designs.

The film tapped four actors to play Steinem at various ages. At times, all of the iterations appeared on screen together, even interacting with each other. Powell used extensive photo references to balance how Steinem looked at particular ages while ensuring each actor “could seamlessly move into the next and make them believably all the same person,” she says.

Designing for the many decades meant Powell had to be an expert in a multitude of well-researched details. Citing a ’70s T-shirt as an example, she says a proper one from the period would have been made from a completely different blend and cut than a shirt from today. So finding “a T-shirt in what looks and feels like the right fabric and right shape is near impossible,” she says.

Powell designed Moore’s long-sleeved ’70s shirt on a tight budget by buying several extra-large men’s shirts and then cutting them up and using the fabric to create another one in the right style. “The simplest things are quite often the hardest to do,” notes Powell. The same was true for the jeans. While it’s possible to find authentic ones from the ’70s, body proportions have changed dramatically. “They don’t fit anybody [now],” Powell says. They had to break down larger sizes and sew jeans from scratch for the right fit.

Similarly, costume designer Susan Lyall’s work on director Aaron Sorkin’s “The Trial of the Chicago 7” involved real-life activists following protests at the 1968 Democratic National Convention.

Lyall jokes that the ensemble cast’s prison uniforms were haute couture because of the amount of work that went into the deceptively simple outfits. The process involved creating patterns, sourcing fabric, aging and distressing the material, and then tailoring each to the actors’ bodies by adjusting pant-leg width as well as sleeve and tunic length.

Through all of that, there were actor considerations, too, since each have “their little quirks of how they want things to fit.

Eddie Redmayne [who played Tom Hayden] doesn’t want to be swallowed whole by a giant uniform.”

Additionally, there were height considerations: Sacha Baron Cohen (as Abbie Hoffman) and Jeremy Strong (Jerry Rubin) have a height difference of approximately 6 inches.

While the 1960s are known for a distinctive style, Lyall strove to ensure the costumes didn’t become caricature. This was particularly important for Cohen since the actor was “concerned that no one think this was just another one of [his over-the-top] characters,” says Lyall, who used photo references to link each of his costumes to the real Abbie Hoffman wearing something similar or identical.

Lyall designed approximately 3,500 costume changes during the course of the film. There were also many extras in the park demonstration scenes and the Chicago police force to costume. With background actors as jurors appearing on camera for days at a time, each needed to look as though they were picking clothes from a full closet at home. The amount of time and effort that went into creating the production’s deceptively simple costumes was “incalculable,” Lyall says.

On Regina King’s “One Night in Miami,” costume designer Francine Jamison-Tanchuck faced the challenge of designing costumes for four frequently photographed civil-rights leaders — Sam Cooke, Malcolm X, Muhammad Ali and Jim Brown — within the context of a fictional story.

One of her favorite looks was the silver sharkskin suit she designed for Sam Cooke (played by Leslie Odom Jr.) to wear during a performance at the Copacabana. The popular fabric blend, so-named for its distinctive smooth sheen, “is indicative of the [time],” says Jamison-Tanchuck.

Despite the many suits in the film, each is designed specifically for the man wearing it. Jamison-Tanchuck did extensive research to fully understand each character. “Before you know it, you’re really into the style and know exactly what they would do and what they would wear,” she says.

Regardless of the decade they set out to portray, the costume designers all had to strike the right balance between historical accuracy and creative interpretation.

Says Lyall: “It takes a huge amount of hunting and searching and creating and devising.”