I picked up today's stitch on Pinterest, the link led me to Misako Mimoko's blog. Eva Monleón from Barcelona is a creative young dollmaker and designer who often promotes hand embroidery.
There is no name for this combination of stitches so I will name it Misako Mimoko Lacing Stitch. Any knowledge of the origin and real name, please let me know in the comment field below.
This is best done on a fabric with a good grid like Aida, or use waste canvas.
Make a row of upright Straight Stitch.
If you intend to do the lacing with a thicker thread, I suggest you stitch over a needle to have more space for the thicker lacing thread.
Make another row parallel to the first.
Remove the needle you have stitched over.
Lace the first thread (light blue) according to the picture.
Change the colour (light green) and lace the second thread.
Notice carefully how to weave the needle over and under the light blue thread.
Anchor at the end of the line.
This example is a little bland - the more contrast between the three threads, the more impact.
Homework:
Add to the samplers.