Commonly, fabric is sewn right sides together and then turned right-sides out so that all seams are hidden. To do this, part of the fabric is not sewn together. This guides gives a suggestion on how to close this seam so that it cannot be seen.
1. Make sure that the raw edges of the fabric are folded inwards so that rounded edges of fabric are pointing upwards. Insert the needle into one piece of fabric.
2. Cross over the seam and insert the needle into the other piece of fabric. The needle should go in and then out of the fabric in a stitch that is parallel to the fabric fold.
3. Return the needle to the original piece of fabric and repeat. Keep sewing stitches that are parallel to the fold back and forth along the sides of the seam until the gap is closed.
I used black thread for contrast, but it’d be a better idea to use a thread that would be better camouflaged. Smaller parallel stitches will lead to a neater seam. Always make sure that the raw edges are pointing inwards!