I love making these. I’ve made two for myself, one for my mom, and put several in my Etsy store. Lined with soft flannel, they will keep the screen free from scratches and the interfacing makes the whole thing hold its shape.
Now it’s your turn to make your own. Put your personality into it! There are so many novelty fabrics that in a very short time you will find several you can’t live without. My solution? Make them all! Also a great way to use an orphan quilt block from a previous project.
Start by measuring your device. Smartphone, slider, clamshell, iPod, iPad, anything. Measure the longer side, shorter side, and depth. For instance, my ancient iPhone is 
approximately 4.5 x 2.5 x .5. Approximate is close enough.Add shorter side twice plus the depth. For mine, that would be 2. 5 + 2.5 + .5, or 5.5. There will be bulk from the seam on the inside, so add a little, plus the fold takes up some bulk, and the seam at the 
top edge.
I’ve been using a 6 inch square, which works just fine, and you can see that the length will fit inside, as long as I take scant 1/4″ seams. You will cut a square of outer fabric, one of fusible interfacing, and one of flannel.
Note: if you have fabric with a one-way design, cut it 1/2″ longer than you need, cut the length in half, lay right sides together and stitch a 1/4″ seam. This will be the bottom of the cell phone case and the bottom of the one-way design should be at this seam. Now your design will be right side up on both sides of your cell phone case.
In this photo, I have highlighted the seam and the direction of the print in green.
Lay the fusible interfacing to the wrong side of the outer fabric and press with your iron. Layer the wrong side of your flannel (if there is one) to the wrong side of the fused outer fabric and interfacing.
Use a strip of coordinating fabric or binding and bind opposite edges of the fabrics.
Fold so that the flannel is to the outside and the outer fabric to the inside. Stitch with a narrow seam at the sides.
Turn.
It’s that easy!
Alternate method: no binding.
For this one I used two smaller pieces of flannel so there is a pieced seam.
Lay fabrics with right sides together and stitch at opposite ends.
Turn and press.
If desired, topstitch at the seams.
Turn outer fabric to the inside and stitch the side seams.
Turn right side out and press.
Quilt in Progress 