After finishing side seams with zig-zag stitch, pinking shears or a serger, keep dress wrong-side facing and finish side vents.
Working one side a time, fold the top corner down to make a triangle and press.
Next, fold the entire tab over 1/4 inch (6mm) and press.
Then fold over a second time, so the folded edge is in line with the side seam. Press and pin in place.
Sew fold, using a 1/4 inch (6mm) seam allowance. Repeat on the other side.
Lastly, working with the right side facing, sew a 3/8 inch (9mm) line of stiches perpendicular to the side vent. This provides added reinforcement. Sew back and forth two or three times.