The actress will star as a prison governor later this month, as glamour girl Mitzeee Minniver (Rachel Shenton) remains in jail for a crime she did not commit.
"It's great and Nicole Barber-Lane (Myra McQueen) was lovely," she said of her time on the soap.
"Despite all the long days and working weekends, she still has a smile on her face - but that's probably down to reading the book Fifty Shades of Grey."
The former Bad Girls actress explained that she quickly found errors in the soap's on-screen prison.
"The noticeboards all had drawing pins. Certain things stick with you and you think, 'Wrong'," she told The Sun.
"You wouldn't have that in prison - it's all stuck up with toothpaste."
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King also stated that she feels the television industry is tough for actresses over 35.
"All of us girls are fighting for the same parts as there aren't that many for those in their 40s and 50s," she explained.
"You are dead in this industry after 35, you start becoming a little bit more invisible. It just means you have to shout very loudly."
King's first scenes will air during the week commencing Monday, August 6.
Hollyoaks airs weeknights at 6.30pm on Channel 4, with first look screenings at 7pm on E4.