SPOILER ALERT: Do not read if you have not watched the 11th episode of “Better Call Saul” Season 6, titled “Breaking Bad.”

When set decorator Ashley Marsh found out “Better Call Saul” was going to revive the iconic RV from “Breaking Bad,” she was psyched. And luckily, the original “Krystal Ship” had been kept safely stored at the Sony lot. There was only one issue: the RV was “completely gutted on the inside.”

Now, “Breaking Bad” had always used two “RVs” — one fully functional vehicle for exterior and driving shots, and a separate soundstage for shooting the interior. To recreate that set for “Better Call Saul,” Marsh “religiously rewatched ‘Breaking Bad'” and took “8,000 screen grabs.” With careful attention to detail, the team had to replace every beaker, tub of methylamine, round-bottom flask and more. Everything we see inside the RV on “Better Call Saul” was new.

“We had to go back and buy everything,” Marsh tells Variety. “We literally just stared at photos until we figured out what these items were.”

To make sure the RV interior looked exactly like it did in “Breaking Bad,” Marsh then set out to find a 1986 Bounder — the same model used for the exterior shots — to gather seats, lights, a mini-fridge door and window coverings. Her search ended with Frank Sandoval, who runs a “Breaking Bad” RV tour company in Albuquerque. (He also appeared in “Breaking Bad” Season 5 as an extra.) After signing an “ironclad NDA,” Sandoval was happy to lend some parts of his Bounder — which shuttles tourists around Albuquerque to fan-favorite “Breaking Bad” locations — to the “Better Call Saul” team.

According to Marsh, Sandoval was the only person they could find that had the exact window coverings shown in “Breaking Bad.” While the typical TV viewer would never notice such a minor incongruity, Marsh says that series co-creators Vince Gilligan and Peter Gould emphasized that fans will inevitably “cut together side by side” the flashback scenes from “Better Call Saul” with the original ones from “Breaking Bad.” “We had to be hyperaware of how right this needed to be,” she says.

What was exciting for Marsh is that this episode of “Better Call Saul” shows the RV interior in a way “Breaking Bad” never did: in motion, with Walt and Jesse preparing to go somewhere. This allowed the set decorators, along with Gilligan and writer-director Thomas Schnauz, to imagine how the meth cooking duo might pack up their equipment for travel. When shooting the interior in motion, the special effects team attached airbags underneath the set to make the RV rock back and forth, emulating driving through the desert.

To reshoot the “Breaking Bad” scene in which Walt and Jesse hold Saul (Bob Odenkirk) at gunpoint in front of a shallow grave, the “Better Call Saul” construction team dug a grave behind the studios in terrain that was similar to the desert, while the greens crew brought in dirt.

Working on “Saul,” as well as 2019’s “El Camino: A Breaking Bad Movie,” Marsh has had her fair share of set-decorating challenges. When “Breaking Bad” introduced Ed the Disappearer (Robert Forster), who runs a witness protection program out of his Best Quality Vacuum shop, the location was a vacuum store in real life, which required very little alteration. When they returned for “El Camino,” it had since been completely turned into a furniture store. So, Marsh and set decoration buyer Rachel Srigley were tasked with transforming it back into Best Quality Vacuum, a process that took three months.

“Rachel was doing research on vacuums to find the exact same models, the exact same colors,” Marsh says. “We cleaned out every vacuum store in town for all of their parts — anything that was close, just to get the volume.”

Nonetheless, Marsh says the trickiest task she’s had in the Gilligan-verse is decorating the department store in last week’s Gene-centered “Better Call Saul.” In the episode, Gene orchestrates an elaborate heist of Armani suits, Air Jordans and linen shirts for cab driver Jeffy (Pat Healy), while distracting the mall security guards with fresh-baked Cinnabons.

“It was an empty Sears,” Marsh says, “with literally nothing inside. Not a rack, no pegs, not one single thing to hang anything on.”

The team had to import tons of couches, racks, fixtures and lamps, as well as “truckloads” full of clothing. Meanwhile, Gene’s rhyming instructions for Jeffy (“One, Armani suits and run! Two, Air Jordan shoes for you!” etc.) served as a guide for designing the store.

It wasn’t the first time Marsh had to build a store from scratch. In fact, between Season 4 and 5 of “Better Call Saul,” the Cinnabon that Gene works at in Omaha (which is filmed in Albuquerque’s Cottonwood Mall) went out of business. Luckily, the production team was able to purchase a lot of what was left — tables, chairs, Coke machines, the massive cake mixer — but Marsh says they nonetheless “had to painstakingly go back and reverse engineer what was missing and put it all back together.” Teaming up with Cinnabon, they were also able to reacquire the specialty oven, dough sheeter and proofers.

“I’m a nerd,” admits Marsh. “Part of why I really love going back and recreating sets is you can really dive in and get excited about things that most people would find boring. It’s like playing a big game of iSpy, but on a professional level.”