Sewing a casing and threading it with elastic is by far the most common and practical way of making waistbands (and wrist and ankle bands) on childrens' clothes. Badly sewn casings with elastic that doesn't sit flat can, however, make your finished garments look a bit ho-hum and amateurish.
Try adding these extra (very simple) steps to sewing your waistbands to lift the look and add a whole lot of professional polish to your finished clothes.
Sew a row of stitching around the top fold of the casing. This adds extra stability to the casing, helps to flatten it out and generally looks more polished.
Sew a double casing. Two is better than one! Here, I've sewn two casings and inserted elastic of half an inch (12mm) width in each to make the waistband. In total you'll have three rows of stitching. The top row as described in Tip 1, a second row enclosing the top casing and a third row enclosing the bottom casing.
Sew the casings in the ususal way leaving a gap at the back of the garment for threading the elastic through. Thread the top casing first, then adjust and sew it closed before threading the bottom casing and repeating the procedure.
Note that you'll get the best result by making the casings just a scant amount larger than the width of the elastic. Too wide and you'll get a baggy look, too narrow and the elastic will pucker and you'll have trouble threading it through.
And if you've ever been confused about the different types of elastic and what they're best used for check out this post:
E is for Elastic (The Sewing Directory blogspot).
I used Knitted Elastic in this project. As you'll read it's not as heavy duty as the Woven variety but still has a lot of stability and a soft handle which is great when sewing childrens' clothes and when using sheerer fabrics like this voile (Valori Wells "Wish" from Hawthorne Threads).
Hope you'll have a go at these tips and let me know what you think!