The first day of rehearsal on Broadway usually goes like this: Circle up. Make introductions. Offer thanks, express optimism, maybe crack a joke. Clear the room of onlookers, and off you go.

But Robert O’Hara had a more pointed agenda in mind when he found himself in a ring of 75 actors and designers and producers one midsummer morning, in a studio lined by a wheelbarrow, a four-poster bed, and refreshments labeled “ dildo cornbread” and “nuts cake.”

Mr. O’Hara is the director of “Slave Play,” Jeremy O. Harris’s raunchy, riveting and risky new work, whose many provocations begin with its double entendre title. Mr. O’Hara, like Mr. Harris and many members of the cast and crew, is black. So with just four weeks to go until the first preview, he ignored the naughtily named snacks and invoked his forebears.

“For many years of my life, I’ve had random white people come to me and ask me about where my last name came from, and I would just look them in the face and say, very politely: ‘Slavery’,” Mr. O’Hara told the rapt gathering at New 42nd Street Studios, quieting the lingering chitchat. “I just want us all to be mindful that it’s because of what our ancestors endured — and survived, and abolished — that we have the audacity to be in this room.”