Oh told GolfChannel.com that he didn't make any changes to Ko's swing as he began coaching in January in Phoenix.
"Her mechanics were already great," Oh said. "It was more fine-tuning things. It was more about sequence, tempo and balance and a lot of practice.
"We worked a lot on her scoring clubs, her short irons and wedges and shots around the green. We spent hours and hours with the scoring clubs."
Oh told GolfChannel.com that they went into a boot-camp-style preparation for the new season after the Kiwi went winless in 2017.
"The days would have been longer, but the sun went down," Oh said.
"I told Lydia I'm very old school, nothing fancy," Oh said. "I said only about 25 percent of my job will be drawing lines on video and that sort of thing, that 75 percent would be about the practice.
"I told her 'I'm not going to tell you how to practice, I'm going to be with you.'"
Ko failed to add to her 14 career LPGA titles in 2017 having a down year for end high standards but still finished second in three events and had 11 top tens across the year.
Ko is aiming to break her winning drought, which goes back to July 2016, this week at a tournament she has won in the past, claiming the 2015 title.
To get the day's top sports stories in your inbox, sign up to our newsletter here
