you need to hold the clutch somehow (up in the air, by hand usually works!), replace the clutch bolt but don't screw it far in. give the bolt head a whack with a hammer and you should be left holding only the clutch.
If you're dissasembling the engine, you can use this method to remove the flywheel and the clutch and seperate the crank case halves at the same time.
Whatever you do don't try and pry the clutch out with a screwdriver or anything or you can bust off the clutch arms. (so they tell me..ahem..)
