I'm cheap and I'd consider making a gasket, but not in this case, too big.
A. Buy the right one.
B. Goop it with some silicone stuff.
My 2 cents.
It is pretty big that's why I asked here maybe someone had a way of doing it that worked that I couldn't think of. Money isn't really the issue I mean 20-30 bucks isn't a huge deal . But if i could get what I need for half that I would rather do that. Maybe I'm cheap.
Don't take me wrong. I thought about how one would make a gasket. A single sheet of material to make a splice-free gasket could easily cost as much the die cut gasket. You'd still have to cut out the gasket, which would be difficult, time consuming and probably require a template to get one that would work. Making the gasket out of strip material would introduce joints in the gasket at the corners. I strongly suspect it would leak at those joints.
Making a valve cover gasket might be done for an antique restoration job, where a die cut gasket wasn't available. It would be done to make the vehicle look factory new and it would be a tedious process.
Yeah, my post was a little flippant, sorry about that.