This is going to be hard to describe.

You take a shortened piece of a Valve Guide; the part with the lip that holds the Valve Stem Seal on; you would have to figure the length.

you Braze that piece of Valve Guide to the thin washer (the washer needs to be like sheetmetal thin so the Valve Springs sitting on top of the washer do not become coil bound) about the outside diameter of the hole that the Valve Springs goes in.

When you install it you put a coating of Silicone Sealant on the Bottom of the washer and slide it over the Valve Stem. Followed by the Valve Stem Seal.

The Valve Spring will sit on the top of the Washer pushing it down and the Silicone will prevent Oil from getting under the Washer. Since the section of Valve Guide is Brazed to the Washer it will not leak there.

The Valve Stem Seal should seal the Valve Stem itself.

The main rub is that the new Brazed on section of Valve Guide is going to have a tigher ID than the old piece of Valve Guide that is still in the Head; so there would be some side ways force exerted on it when the Valve goes up and down.
It would work best if the hole in the Brazed on section of Valve guide was enlarged so it would not touch the Valve Stem so no sideways force could break it off at the Brazed joint.

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