An inexpensive leather punch can be had from Harbor Freight, and will do nicely for occasional use. (A fancy pair of pliers with spines.)
I made a template out of cardboard, and punched the holes there first. Then, marked them on the sides of the skirt, and punched away.
Next, turn it over, and do the other side to match.
Lastly, put a dab of Proofhide in the holes to protect the leather.
If you take your time making a good template, the results will be none less than professional.
And, the old addage of measuring twice, punch once should be heeded - even three times won't hurt.