What you will need:
18" pillow form
1.5 yards of fabric
hand sewing needle
ruler or measuring tape
Okay, first cut a square for your front.
(You'll need one 18.5" x 18.5" square.)
Then, cut your rectangles.
(You'll need two that are 12" x 18.5" for the envelope back
Four that are 22" x 6"
And two that are 2.75" x 5.5")
Sew down both long sides of two of your 22" x 6" rectangles, right sides together.
Turn this piece inside out and press. This will become your bow ends.
Then sew all the way around the edges of your other two 22" x 6" rectangles, right sides together, leaving a 2" open space on one 6" side. Flip this sandwiched rectangle inside out through that open hole, making sure all your corners have been snipped first. Press.
Take these last two inside-out rectangles and sew them into loops by sewing the two 6" ends together for the large rectangle and the two 2.75" ends together for the small rectangle.
Thread the larger loop through the smaller loop.
Now you have a bow!
Now thread your bow end piece through the back of your bow.
Pin your bow along the press line, pinning the ends to the edges of your pillow cover and each of the four corners of the bow. Make sure everything looks even to you.
Flip the pillow cover over and hand sew the corners of the bow to your pillow, making sure to just barely nip the back of the bow...you don't want any stitches showing from the front. I also tack down the center piece of the bow for stability.
Sew along the edges of your pillow cover where your bow overlaps and trim off the excess.
Now take your two 12" x 18.5" rectangles and hem one 18.5" side on both pieces. You do this by pressing .25" over once and then another .25" while your fabric is right side down.
Sew down each of your hems.
Set out your pillow cover, right side up. Pin each back piece right side down onto the pillow cover front. The hemmed envelope ends will overlap each other in the middle of the pillow.
Sew around the edges of the pillow cover. Flip your pillow cover inside out, and you're done!