Swore I'd never do this, but here I go!

The Clawhammer Thumb should idealy rest ON the B String if learning and 'weave' back UP to get and sound the little G string on the next oddnumbered note - if playing equal division -.

I know I said everyone is different, but that little lick cost me 5bucks from one of the finest Southern Clawhammer players in the 1990s, and for me it worked like a charm!

The reason why that one works so well, is that most novices tend to already have learned the basic Frail pattern which requires the Thumb to rest NEAR or on the little G string. So from the start they have an inbuilt problem with timing - always drifting back to the wrong parking place for the thumb.