Rhea Seehorn veers from the darkness of “Better Call Saul” to “Cooper’s Bar,” a short-form meta comedy Web series in which she plays a horrendous Tinseltown executive dubbed “the biggest d–k in Hollywood.”

The series, available on AMC.com and AMC’s YouTube channel, was created by stars Lou Mustillo and David Conolly along with Hannah Davis-Law, Nick Morton and Seehorn — who also directs two of the six episodes and is an executive producer.

It revolves around longtime character actor Cooper Marino (Mustillo), who’s tired of the soul-crushing Hollywood treadmill and longs to return to his native Buffalo with his wife, Mary (Kila Kitu), a therapist. He runs a cozy, colorful neighborhood bar from the backyard of his LA home — which, through a series of events, attracts the attention of Kris Latimer (Seehorn), who wants to shoot a “Cheers”-type comedy pilot about the bar and its denizens … starring Amy Schumer.

Cooper balks at the idea — it’s his life, after all — and the series plays out in a back-and-forth that touches on, among other themes, Hollywood backstabbing and its (often deflating) show-business dealmaking.

“Originally we were going to do a short film with Nick Morton, Hannah and David Conolly, the three creators, and we all know Lou,” Seehorn told The Post. “We used to work out together in this boot camp in Glendale and Lou always had these very funny stories. He’s such a great actor and a great personality … and we started thinking about how we could film these stories.

“He has this backyard that is exactly what you see [on ‘Cooper’s Bar’],” she said. “It’s a fully-realized Tiki Bar — our set designer boosted it up a little — but it was just there and is funny. We did a short [film] and it did well at SXSW [the film festival] and we ended up connecting with AMC and the Bacardi [Rum] people and they wanted to make it into a short series.”

Casey Washington and Conolly play Cooper’s buddies Brandon and David who are, respectively, a wannabe screenwriter/mall cop and a sketchy director who drives an Uber (and introduces Kris to Cooper). There’s also a millennial Web influencer named Billy Canasta (Lechristopher Williams) who lives next door and Antonia (Daniella Garcia), Kris’ ambitious underling who’s got her own agenda.

“It has a lot of silliness and broad comedy but it has these friendships at the heart of it and this band of people finding their own family,” Seehorn said. “We worked really hard on this; there are a lot of meta jokes and ‘inside baseball’ stuff but it’s got those friendship at its heart.

“Kris, my super-villain executive, became this sort of cesspool reception area for every note or issue [with Cooper’s deal] that all three of our writers have had to go through,” she said. “We tried to keep it accessible; even those situations in this business where if someone gets ahead or moves out of their hometown you see that conflict, or when does one give up their dream?

“We tried to include things in the story that felt universal so the whole [series] didn’t feel like one big inside joke.”

“Cooper’s Bar” was shot on-location in Mustillo’s backyard. “We did it for love and we are all friends and we just wanted to make something fun together,” Seehorn said. “I wanted to try directing again after I did Episode 604 of ‘Saul’ [‘Hit and Run’] and this was very different … We had to shoot super-fast because we were in a real-life location and they were mostly all night shoots — we did a few daytime scenes, but not too many, and started to get these incredible co-stars who wanted to come play with us, like Phil LaMarr” [who plays Kris’ boss, Cyrus Long].

“Better Call Saul” returns to AMC for its final six episodes starting July 11 with the futures of Jimmy McGill/Saul Goodman (Bob Odenkirk) and Kim Wexler (Seehorn) on the line with the reappearance of cold-blooded drug kingpin Lalo Salamanca (Tony Dalton), who nonchalantly blew away Howard Hamlin (Patrick Fabian) in the midseason finale.

“There’s no easy way to explain [what happens] and I don’t mean just because I can’t spoil anything,” Seehorn said. “It’s a bit like playing the game ‘Taboo.’ It’s like if there were 30 words on the card and you’re trying to make a sentence. I’ve never seen something so complex, dense and very thoughtful but also very exciting. [Showrunner] Peter Gould has been very carefully sorting out complex milestones that have to be hit and things that need to be answered … it’s not just connecting the dots. It’s much more thoughtful.

“I was mesmerized by how they insisted to be completely true to the characters and advance [the story] forward,” she said. “It’s deeply moving and fraught and suspenseful and terrifying and devastating and very psychological.

“I’m still thinking about what happens in these next episodes.”