Flock has clocked two minutes, 35.80 seconds over her three runs with Britain's Lizzy Yarnold 0.02 seconds behind the Austrian armed forces corporal, while Germany's Jacqueline Loelling, who led the first two heats, was in third.
A gold from Flock would be the first time an Austrian woman has won an Olympic medal in the skeleton. British women have won medals at every skeleton event since the sport was reintroduced to the Games in 2002.
An initially good run from defending Olympic champion Lizzy Yarnold was slowed by a hit against the wall ahead of one of the last curves at the Olympic Sliding Centre.
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(Reporting by James Pearson; editing by Clare Lovell)
