Flatland, part of the Norwegian World Championship winning relay team this year, took just 20:41.20 minutes to complete the 7.5km sprint course, finishing nearly 16 seconds ahead of nearest rival Russia’s Olga Zaitseva, who also shot clean.
Norway's Tora Berger, with one penalty finished third, 22 seconds back while early World Cup leader Gabriela Soukalova come home sixth.
And Flatland, whose previous World Cup win was in 2011, claimed the victory was the best of her career.
"My race was very good; the best race ever because in my first win I had a penalty, and this time I had a better feeling on my skis than then," she said.
Great Britain's Nerys Jones ranked 96th, finishing just over five minutes behind the winner after picking up four shooting penalties.
© Sportsbeat 2013