making a cylinder foot gasket from gearbox gasket paper - I made other gaskets in a similar way.
Where thickness is not crucial, I use leather. The only factory gaskets on my bike are for the heads.
measure diameter and cut very slightly on the larger side
leave the part oily, it serves as 'ink' to mark the paper - run thumb around to 'print'.
... and finish off with punches and scissors.
Mount with Locktite Flange Seal - this will keep things bone dry.