I finally finished up my pleated pillow yesterday and wanted to show you how I made it.
First I measured my thrifted pillow - mine was 17 x17 inches. So I cut out the following:
1 back piece 18in x 19in in yellow linen (I added 1 inch all around for 1/2 seam allowance and an extra inch to the height to add a zipper)
1 front piece 18in x 36 inches in yellow linen
1 front lining piece 18in x 18 in in muslin (this is just to stabilize the pleats and won't be seen)
Back piece :
To attach the zipper I cut horizontally where I wanted the zipper to go - I placed it 1/4 of the way from the top. (make sure you cut the long side not the shorter side of the back piece)
Then I attached the zipper using this tutorial and 1/2 inch seam allowance. Now the back piece should be square.
Set back piece aside.
On the two long sides (starting 2 inched from the top and bottom) I measured every 1/2 inch and put a small mark in the seam allowance. This will make 1 inch pleats. If you want smaller or larger pleats you will need to adjust accordingly.
Now the tedious process of ironing out the pleats. I used a lot of pins and a lot of steam to make them as visually perfect as possible. Keep pleating until the front piece is square and the same size as the muslin lining.
Pin the back of the front pleated piece to the muslin matching corners. Lift up each pleat and top stitch the front linen to the muslin close to the fold. Once the pleat is lying back down you should not be able to see this stitching. It will keep the pleat folded even when the fabric is pulled taut and filled with a pillow.
Now the Muslin should be attached to the front and the front and back pieces should be the same size - 18x18inches.
Open zipper. Pin right sides together. Stitch all 4 sides at 1/2 inch seam allowance and clip corners. Turn right side out. Press. Insert pillow.
And now you have a gorgeous new pillow at a fraction of the cost.