take a very sharp knife and cut the jugular veins on either side of the neck.
This method should always come with a disclaimer to use cut-proof gloves for newbies.
I tried this method for our first attempt and ended up slashing my own tendon on my thumb.
Granted, you may not anticipate such a level of incompetence, but we are out there lol... and even in skilled hands accidents can happen.
The surgeon said it was so thin in that area of the thumb that he couldn't fix it a second time so I had to have it fully immobilized up the arm for ten weeks and partially immobilized after that. Months of physical therapy to stretch it out and get it working again. It's my dominant thumb and impacts my ability to perform certain tasks quickly... such as opening snaps on the chicken gates.
After my accident people on here asked me "why weren't you wearing gloves?" and I was like "what gloves?"

None of the guides that I had studied suggested it.
All of the nurses, doctors, and different physical therapists asked how I managed to perform this doozy and seemed rather appalled that I would try to kill a chicken. Oy.
The crop is pretty much just a storage area. Digestion begins in the gizzard.
Umm, was this directed towards what I wrote above it?
If so, I didn't mention that it was 8 hours before we finally tried the broomstick on him. It was our first attempt with that, and my arm was still casted, so my mom and I worked together and he just wouldn't die (no flapping, just stillness, and then I would see one of his eyes twitch). The poor, poor little roo. We had studied everything we could and watched the videos... but they leave out details of technique and well, some things you just have to learn by doing.
I'm totally scared to cull anything now. But my mom has gotten quite good at it (broomstick) so I just catch them for her and go hide.