Painter Richard Nutbourne hopped off a flight from England last week and headed straight to the New York's Park Avenue Armory to check that the nearly two dozen giant artificial stones he had shipped over the ocean had arrived safely.

"They look a little small in here," he said, dusting off some loose dirt from the 19-foot high slabs of polystyrene and fiberglass with a plaster finish. The rocks had survived the trip virtually intact. Indeed, the 80-foot-high ceilings of the Armory did dwarf the slabs—not unusual for productions playing inside the castle-like structure completed in 1881 as headquarters for the National Guard's Seventh Regiment.

But Macbeth costume and set designer Christopher Oram wasn't concerned. "You don't want them too big," he said. He emphasized that the stones needed to be part of the "human scale" of the set for the new production of "Macbeth," starring Kenneth Branagh in his New York stage debut. The show opens Saturday at the Armory.

The set is as ambitious as the play's main character. It features a giant slab of Scottish heath along Park Avenue, where Macbeth will wage battle against rival clansmen and, ultimately, himself. The full-size "stones" form a henge at one end of the stage. There's a 20,000-square-foot heath through which audience members will traipse to get to their seats, at the far end of the 55,000-square-foot Drill Hall.

Once ticket holders arrive at the stage area, they will climb into rough-hewed wooden bleacher seats on either side of a long narrow pit filled with dirt. During the first scene, it will rain, which will turn the dirt into mud. In this mess, at intervals over the next two hours, clans of Scotsmen will attempt to bludgeon each other to death inches away from the front rows.

"We wanted to present a 'Macbeth' that will be visceral and aggressive and masculine and frightening, and yet also addresses the poetry of the writing," says Mr. Oram, surveying the transformation from Drill Hall to heath. Over the course of 10 days, between 75 and 100 men and women labored to create the massive set. As opening night neared, men outfitted in mountaineering harnesses hung like spiders from the giant metal frame of the bleachers they were constructing; their clanging sounded like swords clashing. A team of workers fabricating the heath rolled gray paint onto the floor, while another group separated moss into clumps.

The stones themselves—painted by Mr. Nutbourne with gesso, plaster, bits of seashell, pumice stone, granite and sand—loomed in the center of the hall as if dropped there by prehistoric Upper East Siders.

Co-directed by Mr. Branagh and Rob Ashford, this version of "Macbeth" is the third major production in the past two years in New York. "We wanted to embrace the Armory space, and use the entire room, not deny it," says Mr. Ashford, who co-directed the play at Britain's Manchester International Festival last summer, where the sold-out production won raves from critics. At the festival, the actors performed in an old church with a mud pit stage built into its center. At the Armory, the creative team wanted to keep the intimate scale of the church stage. The challenge was to fill the rest of the space. That led to the idea of the heath, a swampy patch of land with shrubs, moss, grasses, puddles and hillocks.

A custom-made ancient, mossy "paved stone" pathway runs through the heath, which will lead audiences metaphorically away from the city and into the pagan, earthy world of the play, in which three "weird sisters" predict characters' fates.

To make the heath, Mr. Oram commissioned New Jersey scenic shop Infinite Scenic. Co-owner Valerie Light and her design team first laid down a carpet over the floor to protect it. Then Ms. Light's crew placed plaster molds and pieces of clear plastic on the carpet which would turn into small mounds of earth and puddles. They interspersed grasses in clumps over the floor.

Then six men in plastic suits (to keep from getting dirty) and dust masks drove a diesel truck into the hall via a garage door on Lexington Avenue. They fed a container on the truck with a sound-absorbent and natural fiber insulation product called K-13. They mixed it with water and glue, so it resembled cold, gloppy oatmeal, then sprayed that brew over the floor with a fire hose, forming a muddy carpet of sorts. A team of scenic designers followed behind, raking the muddy mixture into what would resemble earth and dirt; the muddy carpet dried in that shape. "I've never made a swamp before," said Ms. Light.

At the end of each performance, the "rainwater" seeps through the stage mud into a trough below the stage that feeds into a reservoir, draining the stage so it's fresh for the following day.

Shakespeare didn't write stage directions into his plays, an absence that freed Mr. Oram to let his imagination run wild, he said. "This is all out of my head. It's a little insane," he said. "Actually, it's a lot insane."