Will has a thing for boxer shorts lately. I happened to have a large pile of unused ones due to Mr. Riley's weight loss. So now Will has a new, large pile of boxer shorts.
Here's how I did it.
First, cut off the elastic waist band.
Next you will cut the crotch seam open and then the seam up the front, next to the fly. You will have one long piece of fabric with 1 or more seams still together, depending on the boxer style. Fold it in half.
Then lay your pattern on top, aligning the hemmed bottom of the boxers with the hemmed line on the pattern. I also cut off the top of the pattern at the waistline, since I won't be making a casing. I also cut off the fly part of the pattern because I'm not putting in a fly. Simple and easy is the plan.
Cut out your pieces and sew your shorts together. I like this pattern because it only has three seams to sew.
Next you are going to measure your child's waist and cut the elastic band to fit. Put the edges together and sew the elastic into a circle.
Mark your waistband in four even place (see the pins in the picture). Mark four even spaces on your shorts and attach waistband to shorts in those spots - right sides together. Stretch the waistband to fit as you sew it to the shorts. And then you'll have finished boxers.