Step 3: Sew the Ends Together
7) Now you need to work out what part will be the main case and what part will be the flap. Pin the fabric together, right sides in, at each corner, and fold the fabric over the phone with about 5mm extra (to account for the seam) marking where it lands.
8) Leaving a 4mm margin on the 'flap' end, sew around the three edges to the marks you made. On the other end just sew straight across the end.
9) Tip: Trim the corners off at 45 degrees, this will give sharper points once you turn it right-way-out.
10) Turn the case the right-way-out, it will look like this.