maybe putting a snake in a black plastic bag, with a small ammount of air, closing it up so its air tight, and putting it in a cool place like a refridgerator? its dark so as to reduce stress, minimal oxygen to gradually suffocate, and cold to shut down the metabolism. I think this method would make them very sleepy and numb so they wont feel the pain of freezing, like they would in a freezer. as oxygen decreases the snake would get dizzy and pass out, much like being under an anesthetic, its dark so they wont be as likely to panic and try to escape. maybe after being in te fridge for several hours then put it in the freezer to be sure its finished. i dont know its just an idea, any opinions are welcome.