How did you fix your valve cover leak?

You don't.

Cruiser- Clean the Valve Cover mating surface real good. I like stronger % Alcohol in a plastic bottle. Felpro cork gasket. Then do what Rusty said and use a little yellow 3M weather strip adhesive on the Valve Cover surface only. No adhesive on the head side

Yes, all good ideas in posts check valve cover, glue gasket to the cover and use cork. But thinking outside the box, you may have too much crankcase pressure, forcing the oil out into the weakest area. Too much engine blow-by, PCV system not working correctly, bad or incorrect PVC valve, hose sucking shut, carbon build-up in the base of the carb..ect. You can test for this using a pressure/vacuum gauge, using "T" fitting in line with the PCV hose between valve and carburetor. Check your breather cap and hose that goes into the air cleaner with this hose removed do you feel vacuum using your finger. With the car running and idling, does the rpm change if you remove the oil fill cap, if you remove the cap do you see an excessive amount of fumes, oil spit, rpm change, just some things to think about.

Make sure you don't have the dreaded leak at the front of the head that is difficult to find and requires removing the head to fix.

I like to “pooch” the bolt hole a bit so it is flat when the clamping is applied. Kinda like a split washer but I have to side with Dicer.