I had an idea for a while to make a ruched pillow for our bedroom. I have it shown on our guest bed in the pictures but that is only because the lighting is better.
First you need a pillow. I happened to find these rectangular pillows that were $3 each at Wal-Mart and marked as travel pillows. The pillow is 14 "x20". You can use whatever size you want though.
You need to measure the length and width of your pillow.
To get the measurement for the front piece I added 1 inch for seam allowances and then doubled that number. So 21x2=42". The width will be 14 plus an inch for seam allowances. That means I needed to cut a piece that was 15"x42". The pieces of the back will form an envelope closure so you need to allow for that. My width measurement will remain at 14" but the length of the envelope pieces will be 15". This allows for hemming the edge of the envelope pieces and for a generous overlap.
Next you need to hem the back pieces so they will not ravel and will have a finished look. Start by folding the edge over 1/2" and pressing in place.
Next turn the 1/2" pressed edge over again to enclose it and press.
Here it is pressed and pinned to sew. Sew close to the edge to secure.
Next you need to gather the piece of fabric that will be the front. To do this adjust your machine to do the longest length stitch you have. For my machine this is 5.
Stitch the entire length of the long edge of the fabric 3/8" from the edge, repeat again 1/4" from the edge. Do the same on the other long side of the fabric.
Now you need to pull up the gathers using the bobbin thread until the piece measures 21 inches. I had it on my cutting board to determine the length but you can just check it with a tape measure or ruler as well.
Adjust the gathers so they look evenly distributed.
Now you need to finish preparing the back piece. Lay the pieces down overlapping them so they are measuring 21" in length.
Pin the area where the pieces overlap and stitch the edge between the pins to hold the pieces in place.
Now it is time to put the front and back together. Make sure the back piece is turned the right way so the envelope edges will have the nice side showing. (This is your warning, I didn't double check so mine has the wrong side showing on the back). Pin the pieces together and stitch together using 1/2" seam allowance. If you plan on washing your pillow cover in the future you should either serge the raw edges or use a zig zag stitch.
Turn right side out and insert your pillow. You can see my blue pillow stripes showing through slightly since my linen fabric is quite transparent. I need to sew a white cover to help hide them.