I use 11 or 9ga wire as the situation may require an a 32 double ferrule as a whammy:

I use nothing but # 9 wire. A 1/2" driver rod with a U in the end is place about three inches from one end of the wire and is drove in the ground. When you drive it in, the wire fold on each side of the driving rod. I snare very open ground with no trees or brush. I also like to stake as far as I can from the trail I am setting.

When I set trail snares in open(grassy) country in late fall I always drive two stakes(before ground is too frozen)one as a support to tie the snare and the other is a kill stick.
Snaring in open country is futile here in winter because of the snow and wind.

Here's a video. You only need to watch the first 6 minutes.

https://www.youtube.com/watch?v=1nMVmFJsjuM

He initially drills a hole through the re-rod to put the #9 wire through before wrapping it around the stake.

The has another video posted on how to build one.

Watched the whole video. We don't have much open country but I can say that system would work in some spots. Thanks for sharing.