I have seen other opinions but I think the best approach is to load the jaws in a manner as close as possible the the load they will experience when they are in use and machine them in that state. This means that they should be clamped on something toward the front of the jaws not towards the rear.
I simply made some sturdy rings and dowel pins that would fit in the counterbore for the mounting bolts. Put the dowel pins in the counterbore holes and then clamp them down on the ring when the chuck closes. Adjust the size of the ring so that the sliding jaws are something like 0.03" from being fully closed then bore the soft jaws to the size of you stock or a thou or two under. Now when you clamp on the stock you have the best contact possible and any bellmouthing of the jaws has been compensated for.
It is one hell of an interrupted cut but if you try drilling you stand a good chance of getting fragments of drill sprayed around inside the machine because it is still an interrupted cut which drill do not like.
When doing this I normally put it on a G71 with a small D value and wander off and have a cup of coffee.
Don't worry too much about messing them up, you can also bolt them back on a couple of serrations closer in and start again.