Drill from the backside for the first pass. Drill slowly with light pressure to minimize deflecting the drill bit as it passes through the hub. As you drill each hole, drop a acrew into the hole that will pass at least 3/4 of the way through the prop to assure that your jig or prop washer does not slip out of place. Flip the prop over and again drill ...slowly...from the front. Once that's done flip it over on it's back and re-drill the holes one size number oversize. You don't want any pre-loading on the prop bolts The best fit is a drop through to the hub and engaging the holes with no interference with the holes.

Hardware stores used to sell a little contraption that could be mounted on a hand drill to act a little like a drill press. They helped keep the drill motor a lot straighter than most do by hand. If you're going to be using a hand drill, make a little wood jig on the table that will hold the prop and prevent it from moving around. Two pieces of 1x2 nailed to the table just far enough apart to set the prop hub between will do. You'll need to have both hands available for the drill motor and the prop drill jig to maintain as vertical a drill position as possible,

Worst case with a wood or carbon prop is that you might end up plugging a hole with a tight fitting wood dowel and have to start over. Don't worry, the hub integrity will be fine if you have to do this as long as the wood dowel is a tight friction fit with a little ca wicked over it from both sides to permanently secure it.