I should imagine you make the box pleats as you would any time on the waist. The waist is made up of 2 pieces. Find the centre and decide if you want the top of pleat there of th,e fold. I would suggest the fold . Now measure the distance from one side to the other and work ou.t how many, pleats. And size of each. If you do a 4 inch top of pleat each pleaT will contain 12 inches of fabric.Half of waist is 16" you can do 4 pleats across front of band. So will need aiece of skirt fabric 48".
Don't know if this will help or not.