In spiral couching, the laid thread is tied / couched to the fabric in a spiral pattern.
The laid thread (blue) is usually thicker than the couching thread.
The thread will be couched 4 times in each circle initially. Later, as we move away from the center, the thread will be tied to the fabric 8 times.
I have folded the blue thread into two (for additional thickness) and anchored it in the middle like shown below.
Start couching by coming up the fabric and passing over the laid thread and going down.
Come back up in the next spot where the thread will be tied down.
Repeat the steps.
As the circle grows bigger, I am increasing the number of times I couch the thread in each round.