I had a photographer request this specific pair of pants (pattern is designed by Crochet My Love and can be found HERE) but with a drawstring. I've done this before and had others ask how I did it so I thought I would write up a quick tutorial that will hopefully be helpful to them and others that may be curious too.
Now there is probably more than one way to do this but this is how I do it...
You are going to start with your completed pants, skirt, bottom of shirt - whatever and add a waistband.
R1: Sc all the way around, join with your 1st sc, ch 1.
Before beginning round 2 you are going to look at the front of your project and decide where you want the openings to be for your drawstring. They are each going to be 2 stitches wide. So space them so that they are close enough together that you can tie them but are still centered. Mark them with stitch markers.
R2: Sc in each st around. When you come to the stitch markers, ch 2 and skip those two spaces. Sc the rest of the way around and join to 1st sc, ch 1.
R3: Sc in each st around with 2 sc in the ch 2 sps, join to 1st sc, ch 1.
R4-7: Sc in each st around, join to top of 1st sc, ch 1. (On row 7, join and break yarn.)
Measure around your waistband and decide how long you want the drawstring to be. Don't forget to include the length of the drawstring hanging out of the holes on the front of the pants.
Make a base chain to match that length, and slip stitch back across it. Break yarn and weave in ends.
OK!!! Now it's time to put it all together. Make sure that you have weaved in all your ends before you begin.
You are going to poke the ends of the drawstring through the front of the pants and line the rest of the inside of your project with the drawstring as shown.
You are now going to fold the waistband over the drawstring and use a yarn needle to secure it down over the drawstring.
Continue all the way around and finish off.
There you go! You now have a drawstring waistband!! WOOT WOOT!!