Pillows have a greater impact on quality of sleep than most people realize. Depending on the way you sleep and whether or not you have shoulder or neck problems, a flat pillow may suit you better than a fluffy one. If you sleep on your side or back, a fluffy pillow provides good neck support. However, if you sleep on your stomach, a flat pillow is more beneficial for you. Pillows used as seat cushions should also be flatter than their decorative counterparts.
Things You'll Need
Heavy object (large book, bricks)
Use the pillow for a while -- it will naturally start to lose its loft after a few weeks.
Lay something heavy on top of the pillow. A large book, a heavy box or a couple of bricks wrapped in a towel will flatten a pillow after a few days.
Cut the pillow's seam on one side with a seam ripper and pull out as much stuffing as necessary in order to make the pillow as flat as you want. Sew the seam closed.