Things You'll Need
Sewing machine or needle and thread
Pillow thickness is a personal preference and flat pillows can be somewhat difficult to find in stores. Flat pillows are idea for stomach sleepers, as a fluffy pillow will tilt your head at an unnatural, uncomfortable angle, resulting in stiffness, muscle spasms and even insomnia. Polyester pillows are very prone to flattening, so they can be flattened by compressing the pillow. If the pillow is still too fluffy, remove a bit of stuffing until it's sufficiently flat.
Flattening a Pillow Using Compression
Place the pillow inside a pillowcase to protect it from dust and debris.
Lift the bed's mattress and place the pillow at the center of the bed, between the mattress and box spring.
Leave the pillow under the mattress for 48 hours. If the pillow is creating an uncomfortable lump in the bed, reposition it before you go to sleep at night.
Lift the mattress and remove the pillow. The pillow should be significantly flatter. If it's still too fluffy for your taste, a bit of stuffing will need to be removed.
Removing Stuffing to Flatten a Pillow
Remove the pillowcase and examine the edges of the pillow to find the visible seam. Most of the seam will not be visible since it was sewn inside-out, but there will be a small section of stitching that was used to close the pillow after it was stuffed. Some pillows have zippers. Unzip the zipper to access the stuffing.
Remove the visible section of stitching with a seam ripper. You need to open the pillow enough to fit your hand inside.
Remove some of the stuffing until the pillow is sufficiently flat.
Place a pillow case over the pillow and sleep on it for a few nights to ensure that it's suitable. Add or remove additional stuffing as needed until the pillow is the perfect thickness.
Remove the pillow case and sew the open seam closed. Tuck the raw edges of the fabric inside the pillow and sew it closed on a sewing machine or hand-stitch it using a hemming stitch or running stitch.
Place the pillow in the clothes dryer for a few minutes if you over-flatten the pillow. This will fluff it up again. Sleep on the pillow for a few nights before sewing it closed. Keep the stuffing in a bag in case you need to replace it in the future. Polyester pillows are very prone to flattening over time, so it may be too flat after a few months of use.