Fold down the waist 2" to hem. If you put on buttonholes, make sure that you are stitching below these. Straight stitch all the way across. Thread your drawstring easily by attaching a safety pin to the end.
If you are inserting an elastic waistband, straight stitch all the way around until you are 2" from your starting point, leaving an opening to insert the elastic. Use a safety pin to thread your elastic through the opening and all around the waist. Stitch the elastic ends together. Finish stitching the waist closed.
Finally, all you need to do is hem the bottom.