I like to use the yellow 3M trim cement, the stuff we called "Gorilla Snot" around the dirt tracks, to attach the cork gasket to the cylinder head, and spread a thin coat of wheel bearing grease on top. That allows the valve cover to be removed and replaced during a lash adjustment without damaging the gasket, and the gasket forms a shallow dam to prevent oil leaks down the sides of the engine when the cover is off for any reason. It takes a little effort to remove the old gasket the next time it's replaced, but it usually survives several on/off procedures before that happens. Be sure to use spreader bars at the bolt holes to prevent compressing the gasket in a narrow area with the bolts.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!