It is not uncommon for my clutch disk to affix itself to the flywheel during storage.

I release it by...
warming up the car in neutral;
shut it off;
have it pointed in a direction with nothing in front of it (like out in the street);
put it in first;
hold my foot down on the clutch;
start the car (it will lurch forward);
keep my foot down on the clutch;
gently ease on and off the gas;
eventually it "pops" free with a godawful bang.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig