Blocking is the process of shaping your finished knit or crocheted garment into a desired shape. When using a thicker yarn like wool or alpaca, wet blocking, or submerging the garment into water and then shaping, works well, but when you are working with a delicate yarn, like cotton, steam blocking is your best option. The key is to force steam through the garment without applying direct heat or hot water, which can damage the cotton.
Pin your garment into shape. Using safety pins shape your garment into the form you would like it to take. Pay attention to any seams or edges that are lumpy or uneven. This is your chance to smooth them.
Wet a pillowcase in clean room-temperature water. Ring the pillowcase out until it is damp and there is no excess water.
Lay the damp pillowcase on top of the pinned garment.
Lightly press a hot iron over the pillowcase to force steam down into your garment. Continue pressing until the pillow case is dry.
You can use the steam function on your iron, but make sure that you don't hold the iron too close to the garment or drip water onto the fabric.