This probably falls in the annals of me missing the obvious, but I’m putting it here for future reference so at least I won’t miss the obvious twice, and also noting this method of rounding the corners. When I started adding the interlaced running stitch border to the carnation needle book, it looked wrong. After some experimentation I got it looking right. It all came down to which way the needle was pointing.
To make this stitch, you start with two parallel lines of running stitch:
The instructions I used said to lace the thread through the stitches, so that’s what I started out doing. After looking at that picture, I pointed the needle outside-in, or always toward the middle of the stitches.
Then, for the second round of lacing the running stitch, I took the needle in the same direction, outside-in.
It looks fine, but it’s not what I had in mind. On closer examination, it looked as though the lacing needed to align differently. So I did the initial lacing the same way, outside-in:
But for the second round of lacing, I went inside-out, or pointing the needle from the middle of the two lines of running stitch toward the outside.