Wilson has now told The Sunday Times: "Since #MeToo... intimacy coaches are really scientific about sex scenes.
"But before nothing would be said. It would be about making it up as you go along.
"No one wanted to discuss [sex scenes], so the actors were invariably left to create something on the day and that’s desperately awkward. It’s a horrible place to be."
The His Dark Materials star quit the US series in 2018 before the final season.
The Affair also starred Maura Tierney, and Joshua Jackson. Anna Paquin joined the show for the fifth and final season after the departure of Wilson, playing her character’s daughter as an adult.
Wilson has continued to be outspoken about the objectification of stars on screen.
She previously told The Edit magazine that it is "unfair" that women are made the focal point of sex scenes the majority of the time, as men's genitalia are rarely shown on screen.
Wilson said: "I kept insisting, 'Why have I always got to do the orgasm face?' There should be a male orgasm face. Why is it always the woman who's orgasming? Let's analyse the male orgasm."
She added: "Women have to provide the titillation because penises can't be seen on screen but breasts can."
When Wilson left The Affair ahead of the final season there were reports that the show’s creator and executive producer Sarah Treem put pressure on cast members to take part in sex scenes, creating an uncomfortable feeling on set.
The Oslo star said in 2020: "There's a lot of noise and anger surrounding it, and really the power rests with me to choose how I discuss my life and my experiences.
“What's important to say is that I did speak up. I did have a voice. I did stand up for myself. There was a situation on The Affair where things didn't feel right, and I dealt with them, and I managed to protect myself.”
Watch: Ruth Wilson in the trailer for HBO thriller Oslo