Although he spent years renovating every corner of the sprawling Château de Fabrègues, Pierre Yovanovitch’s favorite thing about his country house is not actually its interior. When at home in the South of France, the designer likes to spend most of his time outdoors. More days than not, he starts his mornings taking his three sheepdogs for a walk around the grounds, past the small, freestanding chapel and through the Louis Benech–designed yew labyrinth. He will pop out again later to feed the chickens or do bits of gardening. “I’m mostly a nervous person, but in my garden I’m calm,” he says, speaking over a video call from his home office, which overlooks the estate. “It’s where I get to disconnect and be a dreamer.”

With his studio working on 40 active projects acr...