Lawrence revealed on The Graham Norton Show that Ramsay challenged them to take interpretive dance lessons for their roles.
The actors found the situation humiliating, which escalated when Ramsay asked them to perform the dance naked on their first day of filming.
Lawrence, who plays a woman experiencing postpartum psychosis, drew on her own 'isolating' postpartum experiences for the role, having been in early pregnancy during filming.
The film, released on 7 November, received rave reviews at the Cannes Film Festival, with critics praising Lawrence's performance as career-best.