Back in the 80’s, when I used to daily drive an aircooled VW, I would use spray adhesive to glue the cork gasket to the valve cover. I would then smear a little grease on the exposed side and install. Spray adhesive, when used properly, sticks great, the gaskets don’t get sucked in and can pop the covers off and on a few times before the cork needs to be changed. YMMV.