In the groove - where the spinner nose cone goes in the back plate.
Drill a very small hole, press or hammer a small stiff piece of music wire, it doesn't need to be may 1/8 - 1/4 inch.
Then take your dremel with a cutoff disk and notch out for the music wire, I usually do a couple, one on each side of the prop cutouts.

I do this on my F1 race planes, not so much for prop moving, but we use large starters on the spinner and they will make the spinner cone cut into the prop without this.

If you still don't get it, let me know and I will upload a couple of pics.