Yesterday evening we had a discussion in the Facebook group about the stitch path for the first row. You need three separate passes. You can work them from right to left or left to right.
You CANNOT carry your thread on all three passes. With certain combinations you can carry your thread once. This is due to how you need to finish the stitches at the beginning and end of the row to replicate MH’s stitching.
The dotted grey line represents the stitches automatically laid on the reverse as you lay the stitches on the front.
The second diagram shows the back if you turned you work over horizontally rather than vertically.
I found starting and ending with a minute pin stitch the easiest using 100/3.