If you look at the instructions for overcasting stitch in your instruction book (figure 9 in the modern books) you'll see that it says to make 2 stitches in each double loop at the edge of your piece of weaving.

However, if you make three stitches in each loop at the spots shown in the image below, you will be able to hide any diagonal threads on the right side of your work, thus giving a much neater finish.