they were probably pre-shrunk when they were made- you can (test) to see if they are (done) by just clipping a little corner- does it fray? if not they have been washed/shrunk enough.
i work with wool alot- i usually just use my water as hot as it gets out of the tap-then i turn on my tea kettle and add hot water to the washer as the water cools down. i make sure to have good agitation - sometimes it takes an hour- sometimes wool will felt/shrink fairly quickly-
rinse in cold (never heard of using ice cubes- plain cold water has always worked just fine- then into a hot dryer