Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

In this tutorial you'll learn how to update any pillows with these great geometrical shapes to make a fresh and updated pillowcase. Since Terial Magic takes the stretch out of knits, feel free to use knits or even t-shirts for a personalized look! 

Cool Geometric Pillowcase Easy Bias & Zipper Sewing

With the emergence of warm weather in Northern California I am in the mood for redecorating. I had some very tired looking shams on some decorative pillows that were made about 10 years ago and needed a lift. After falling in love with some geometric style pillows on Pinterest, I decided to create something of my own.


  • Terial Magic
  • Sewing Machine
  • Scissors
  • Straight Edge
  • Invisible Zipper
  • Fabric: Knits or Wovens

Step one: Apply Terial Magic

Because cutting fabric on the diagonal (bias) and working with knits can sometimes be tricky to sew, as it can stretch and even tear, I decided to use Terial Magic as a stabilizer to resolve that problem. It worked great! After treating Terial Magic according to the instructions on the bottle, I started by cutting three squares the size of my pillow, plus one inch for seam allowance. I ended up with extra fabric, but this seemed the easiest way to do it rather than getting out a compass!

Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

Once I had the three squares cut, I started with one square and created a pattern. Next, I eye-balled it - you can do that too, as there are no wrong dimensions here - using a ruler and a chalk wheel to make a straight line from one side of the fabric to the other.

Step two: Cutting the geometric pattern

Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

Then I cut with scissors. Once the first cut was made, I was able to eye-ball the second cut to form a geometric pattern.

Step three: Pick your fabric and cut

Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

After deciding which fabrics to go where, I used the pattern I made as a template to cut out the rest.

Step four: Sew without pins

Geometric Pillowcase Fabric Patterns

Because Terial Magic makes the fabric paper-like, it doesn’t slip as much and is much easier to sew without pins, so go for it!

Step five: Iron flat

Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

Once you have sewn the triangles together turn over and iron seams flat, the press easily and lay flat with ease, again because of the Terial Magic. If you haven’t tried it yet, get some for this project!

Step six: Creating the back of pillow

Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

Now for the back. I decided to keep it simple since the front has three different fabrics. I wanted to keep the lines going so I cut out a square the size of my pillow (plus one inch for seam allowance) and then cut it into two triangles which I then sewed together.

Step seven: How to sew the invisible zipper

Cool Geometric Pillowcase with Easy Bias & Zipper Sewing!

The trickiest part: sewing on an invisible zipper. Zippers have always been difficult for me, until I tried it with Terial Magic! The stability the Terial Magic adds to the fabric really helps keep the zipper stay in place and prevents bunching. Also, there is an invisible zipper foot you can buy that helps make it so that it stays truly invisible, but I ordered three and they were all the wrong size, so I was forced to use the normal zipper foot. If you’ve never done this before, I highly suggest looking it up online or watching a YouTube video. Sew the zipper onto one side of the front or the back. I suggest putting it on the side that you will most likely use as the bottom of the pillow.

Continue with the other side and then finish sewing the perimeter of the pillowcase, making sure the zipper is open so you can turn it inside out. Clip the corners and then turn inside out. Wash the pillowcases carefully - maybe even do it by hand.

Geometric Pillowcase Using Scrap Fabric

In conclusion: Go play!

The great thing is that there is a lot of variety possible here so feel free to play with the pattern and the fabrics. Hopefully they will add a little pop of brightness to your decor, as they did to mine!

Next Project: Adorable DIY Fabric Faux Fruit