His slippers are tucked under the drawing table, the watercolors and colored pencils just where he left them. And wild things — creature toys and posters — lie all around.

Maurice Sendak died six years ago, but his spirit lingers in every corner of the rambling retreat where he lived and worked for nearly 40 years. Since his death in 2012, at 83, his Ridgefield, Conn., home has been off-limits to the general public, but that’s about to change: On Thursday, the Maurice Sendak Foundation announced — over cake, Sendak’s favorite food, at the New York Public Library’s Fifth Avenue flagship — that it would welcome visitors starting next year.

But why wait? Foundation president Lynn Caponera and writer Arthur Yorinks — Sendak’s longtime caretaker and his collaborator on several books, respectively — led The Post through his home and grounds. It’s also his ­final resting place: Sendak’s ashes, along with those of his partner of 50 years, child psychiatrist Eugene Glynn, and those of their dogs lie ­under the pachysandra, to the right of the driveway.

All told, it’s a relatively humble place for Martha Stewart country, in a bucolic corner of Connecticut five minutes from West­chester County. From its newly sprouted, mushroom-shaped, climate-controlled archive to the 1790s farmhouse that is its heart, Sendak’s house is a historic hodgepodge. The kitchen, with its peeling formica counter, dates from the 1950s.

“Maurice wasn’t into fancy,” said Caponera. Now 58, she started working for her famous next-door neighbor 47 years ago, weeding the lawn and overseeing a succession of German shepherds. (Herman, the author’s last dog, died two years ago.) Sendak drew her 11-year-old self to illustrate a story in “The Juniper Tree,” a 1973 book of Grimm’s fairy tales.

Passing by the old refrigerator, Caponera recalled how she and Sendak used to grow vegetables and freeze them. Though he stopped cooking in his later years, “He was a very good cleaner-upper. He’d invite people to dine and tell them what to bring,”

Mostly, Yorinks said, that something was cake — the nominal subject of “Presto and Zesto in Limbo­land” (Michael di Capua Books), the children’s book he and Sendak started 15 years ago, before moving on to other things. After Caponera found the pages in a studio drawer, she urged Yorinks, now 66, to finish it. The book, about two friends who stumble on adventure when they go looking for pastry, came out earlier this month.

“He had a whole network of neighbors who’d bring him cake,” recalled Yorinks, who used to ride the train from New York with Sendak’s favorite, “a big fat chocolate cake from Sutter’s Bakery,” on his lap. Caponera said she used to fish out crumbs from Sendak’s paint bottles. Again, nothing fancy: The paints were from Rich Art, the brand he had used as a boy.

Until his death following a stroke, a month before his 84th birthday, Sendak adhered to an unvarying schedule. He’d rise at 9 a.m., tuck into breakfast — it was ­always an English muffin with Dundee preserves and green tea — then step into his studio, a few feet from the kitchen, to check correspondence. Next came an hour-long dog walk, no matter the weather or his health, followed by a viewing of the soap opera “All My Children.”

After that, he’d return to his studio for a few hours before breaking for cake, a nap and dinner before heading back to work. Often he’d stay in his studio until 3 in the morning, writing and painting to music, mostly Mozart. A small room between kitchen and studio, once used for laundry, still brims with CDs, nearly all of them classical.

The next day, he’d do it all over again. “It was that kind of routine,” Yorinks mused, “that let him fly into the chaos of creation.”

When Sendak wasn’t working, sleeping or noshing, he was collecting — just about everything, especially anything involving Mickey Mouse, who entered the world in 1928, the same year he did. Several cupboards are filled with Mickey memorabilia, including entire sets of mouse-embossed dishware, a bank, even an ashtray.

And then there are the paintings — some, by Rembrandt and William Blake, now tucked away in a vault — and drawings by himself and his friends. The Jules Feiffer cartoon hanging in a first-floor bathroom is inscribed, “To Maurice, with love, admiration and self-pity.”

Sendak filled his house with what he loved: painted furniture, hooked rugs, Judaica and toys, both those inspired by his books and the ones he had as a child, like the Buck Rogers windup plane he kept in the dining room, near the Tang Dynasty ceramics.

Here and there are oddities, like the wooden box in the living room, underneath the Steinway grand. (Sendak didn’t play the piano, but his partner did. “Maurice,” Caponera said, “was a champion whistler.”) Riddled with holes, the box once held a circus’ rattlesnakes.

On a chair nearby is a puppet a friend of Sendak’s made of Jennie, his late, adored Sealingham terrier whose successful afterlife he imagined in “Higglety Pigglety Pop! Or There Must Be More to Life.” That beautifully drawn book (the illustrations for which now sit in the archive) came out in 1967. Some six years later, Sendak’s doctor suggested he find a place in the country, Yorinks said, “to relax.”

Sendak’s lawyer found the house at 200 Chestnut Hill Road, and the artist moved in 1973. With rare exceptions, he spent the rest of his days there.

He willed his home and nearly everything else to Caponera. “He kept saying, ‘You’ll know what to do with it,’” she said. She did, turning some of the land into a conservation for black bears, red fox and all kinds of wild things.

“People called him a curmudgeon, but he really wasn’t,” she said of Sendak. “He was opinionated, but never hurtful. Anyone who came into his house, [whether] plumber or artist, was on equal terms.”

Sendak would have been 90 this year. Time enough, she said, to open his house to readers of all ages, “and keep Maurice’s legacy alive.”