Bulk Up raises up his defense and attack, while Hone Claws raises up his attack and accuracy.
EVs: not yet decided
- Low Sweep
- Giga Impact
- Bulk-Up/Hone Claws
I would suggest that you ditch Slaking and get yourself a Kangaskhan using Bulk Up over Hone Claws. The only attack that Slaking really has to worry about missing is Giga Impact, so the added bulk of Bulk Up can help you survive more than the accuracy boost of Hone Claws.