About 2 and 1/2 to 3 hours I think.
A lot of the time was getting the snow in a pile. The snow was all hard, crunchy and non-sticky on the top - so I had to scrape the top layer off to get at the sticky snow underneath. That took ages.
(
Pandemonium in my underpants,
Sun 27 Jan 2013, 3:10,
archived)