It has the attack boost for fling, but the next turn it will lose the attack boost.
No sorry Jofly, once thrown away with fling it doesn't get attack boost from the thick bone anymore, I have tried it before... EPIC FAIL. But it is good to use as a finishing move. Chances that your opponent would survive such a monstrous attack is very little(except if it has a resisting type but still, it would do massive damage).