"It never gets old and it never gets easy," Clark told a crowd assembled for the team-naming ceremony after the competition.
"This is one of the greatest privileges of my life."
Clark, the most decorated women's snowboarder of all time, scored an 89 on her first of three trips down the halfpipe.
The 17-year-old Kim, who has called the 34-year-old Clark a mentor, scored an 87 on her second run but was unable to catch Clark.
Kim had already secured her spot on the U.S. team prior to Saturday's competition and did not attempt some of the more challenging tricks that have made her a favourite to win gold in Pyeongchang next month.
Korean-American Kim said getting the chance to compete in South Korea for this first Olympics added an extra layer of excitement.
"I have family in Korea as well so this has a special meaning to me," she said. "I am really excited for these next couple months. I think it will be a good time."
Clark and Kim will be joined by 17-year-old Maddie Mastro, who finished third, with the fourth spot yet to be determined, but is likely go to 21-year-old Arielle Gold.
Chase Josey scored an impressive 94.5 on his first run to win his first Grand Prix and make a strong case to be given the fourth spot on the U.S. men's snowboarding team for Pyeongchang.
Ben Ferguson, Shaun White and Jake Pates had all already qualified.
Only Ferguson competed on Saturday, looking explosive on the course but finishing second to the 22-year-old Josey.
Two-time gold medallist White had been expected to compete on Saturday but withdrew due to illness.
White booked his ticket to Pyeongchang last weekend when he scored a perfect 100 to win at the U.S. Grand Prix in Snowmass, Colorado.
White was on hand for the competition on Saturday and said his enthusiasm was running high ahead of his fourth Olympics.
"I am so excited because it is not easy," he told a press conference. "I'm pumped."
A scary moment came when veteran American Danny Davis crashed towards the end of his second run, landing hard on his back at the top of the railing before skidding to the halfpipe floor.
After being treated by medical staff for several minutes he walked off unaided, earning loud applause from the crowd.
(Editing by Greg Stutchbury and Sudipto Ganguly)
