To keep the waist even, you’ll need to take in the same amount of fabric from each side seam. For example, you might want to take in a dress by 1⁄2 inch (1. 3 cm) on each side so it fits better.
Pin about every 1 inch (2. 5 cm) or so all the way down to the narrowest part of the waist. Ensure that each pin goes through both sides of the dress.
If the waist is still too loose, adjust the pins to take in more fabric. If the dress feels too tight, consider letting out some of the fabric at the waist.
Taking in the side seams to the waist will prevent the waist from puckering when you remove the excess fabric.
Although you could take in the dress by hand, a sewing machine will make stronger, more uniform stitches.
Read the care label for the dress to see if you should iron it. This can give your dress a more polished look.
Place the belt where you’d like the elastic casing to be.
Since it can be hard to reach around, you may want to ask a friend to help you with this step. The fabric chalk should dissolve when you wash the dress.
It’s important to use your own measurement instead of relying on size charts. Size charts that pair waist measurements with sizes can vary wildly.
For example, if your waistline measured 38 inches (97 cm), cut the strip 39 inches (99 cm) long and 1 3⁄4 in (4. 4 cm) wide.
To make it easier to sew, consider ironing the strip of fabric so it stays flat. You should now have a casing that looks like a long, thin tube.
If you’d like the casing to lie flat, you can iron it once it’s right side out. You can remove the safety pin once you’ve turned the casing right side out.
Try to pin every 1 to 2 inches (2. 5 to 5. 1 cm) so the casing doesn’t slide around.
If your machine has one, use an edge joining foot. This foot will act as a guide as you edge stitch along the casing.
To prevent the elastic from slipping back into the casing, you can pin the ends to the fabric outside the casing. At this point you can try on the dress right side out to see if you’re happy with the waistline.
