The ladder stitch, which can also be called a blind stitch, is a hand sewing technique that usually is worked on the right side of the fabrics. It is often used to close gaps left when you turn something right sides out.
Tie a small knot at the end of a length of thread and thread it on a needle.
Pull the needle from the wrong side to the right side of the hem’s fold so that the thread’s knot is hidden.
Insert the needle directly across from the first exit point and push the needle along the opposite fold, picking up about 1/8 inch of fabric.
Go back and forth like this, sewing through the folds until you reach the end of the gap. Tie a knot at the end.
Pull the thread through the layers of fabric and snip it at the exit point to hide the end.