val source = flow {
        emit(1)
        delay(200)
        emit(2)
        delay(200)
        emit(3)
    }

source
    .onEach { delay(500) }
    .collect {
        ...
    }

1 - 500ms
2 - 700ms
3 - 900ms

source
     .onStart{ delay(500) }
     .collect {
         ...
     }

Flow

launch

collect

coroutineScope {
    source.collect {
        launch {
            delay(500)
            //Move original collect code here
        }
    }