Left hand bass can take many forms. LHB for a jazz organist is quite different than say stride piano or even (solo) coctail piano. Except for some transcribed 'ragtime', it's hardly ever written down. That's because it's more a technique or playing style than it is what one would see in a normal piece of sheet music. I still think critical listening to a style that you like is the best way to learn this hard to define aspect of playing non-classical music. JMO.

chas