Diagonal hem stitch
Prepare for diagonal hem stitch by following one of the drawn thread removal techniques: Drawn thread preparation or Drawn thread preparation with buttonhole edges.
Cast on in the overwoven end, count four threads along and bring the needle up.
Go back over the same four threads and take the needle down.
Count four threads along and bring the needle up in the same place again.
Pull the working thread tight to draw the threads together.
Count into the fabric by two threads and take the needle down, while holding the working thread tight to keep the threads gathered.
Continue and count four threads along. Bring the needle up ready for the next stitch.
Continue all along one edge.
For the other edge work the same method, but stagger the gathering stitch by bringing the needle out just two threads along for the first stitch, and from then on gather four threads together. The last stitch will be just two threads to gather.
A sample of diagonal hem stitch.
Various Authors, The Royal School of Needlework Book of Embroidery (2018) , p.338