Locate your hole pattern (or bosses) on your mill......

with pilot holes reamed to standard dowel pin size and use your tailstock chuck to rough locate in your four jaw. You can then indicate the dowel. Difficulty comes in trying to make the holes perpendicular to a surface in a cheap chuck, especially if you are boring multiple holes. Invest in a boring head when you can.

"Silence is the only thing that can hinder the Truth"