While researching bandana pants I came across this tutorial.
I use elastic instead of twill tape.
To replace with elastic: measure the waist of the child. Add an inch, cut that measurement from elastic.
Thread the elastic through with a safety pin.
When reaching the other end overlap the elastic by an inch and sew together on both sides using a zigzag.
Pull the elastic so that it goes into the waist and sew the waist closed (I only have two hands and one was used to take the picture. You would use both hands to pull on the waist so that the elastic would pull in.)
And there you have it, a quick pair of pants that take about 15 minutes to make and cost (with elastic) around $2.25 a pair. I added rick-rack to make it girly for my niece. Adds a nice touch doesn't it?