It is illegal to kill snakes as they are protected. However they can be killed if they endanger humans or stock (or pets). So I will obtain a carcase, and maybe put it in the fridge or freezer

if it is not needed yet. Then use it to mark a scent trail. Better fresh. If the dog, needs to be older, scents it and follows their trail, you discourage them, or tell them no. When the dog is much older if necessary I will use an electric collar to give the discouragement message. Maybe let the dog come across the snake and then zap him if he shows any interest.

Siegfried was very frightened of snakes and when scenting them would jump back. But then he would follow-up their scent which is not good. As a nine month (?) old pup he was struck in the shoulder by a brown snake but somehow the snake never got the fangs in. Probably at the extreme reach of the strike. Definitely a lucky dog and he certainly used up a life with that luck.

This is just my own method. I will have to see if anyone else has any other methods.