it seemed an NE555 can be operated as a RS flip flop, bistable
https://electronicsclub.info/555bistable.htm

a JK flip flop, it seemed, however, that a clock is needed for it to work like an RS flip flop
https://assets.nexperia.com/documents/data-sheet/74HC_HCT109.pdf
is there a 'common' way to use a JK flip flop as like a RS flip flop? e.g. without the clocks?

 

You can use the asynchronous clear and set inputs, but that largely defeats the purpose have having a JK flip-flop in the first place. It also opens you up to the very demons that motivate using a clocked flip-flop.

 

i'm thinking of a 'lazy' way to use a JK flip flop as JK flip flop has well defined states, just that it needs a clock train to work well

 

i'm thinking of a 'lazy' way to use a JK flip flop as JK flip flop has well defined states, just that it needs a clock train to work well

Taking the 'lazy' way is a good way to awaken those demons.

 

is there a 'common' way to use a JK flip flop as like a RS flip flop? e.g. without the clocks?

You can use the Set and Reset inputs as noted, but then you are just wasting the use of a FF where an RS latch is all you want.
An RS latch and a clocked FF are seldom interchangeable in a real digital circuit application.

i'm thinking of a 'lazy' way to use a JK flip flop as JK flip flop has well defined states, just that it needs a clock train to work well

A clocked FF doesn't need a clock to "work well" it needs a clock to preform a specific logical clocked function, such as in a binary counter.
Your "lazy" way is just using the FF as a latch, which means it is no longer functioning as a JK flip-flop.