@lelimlley first of all, welcome to the forums
This has been a concern of mine as well. I have opted to carefully pick them up with paper napkins or tissue and pop them in the freezer, i don't think they are traumatized, i don't think they feel the cold, i think they just go to sleep and eventually die. The frozen ones go out with the garbage.
To prevent the slugs from eating my plants I use copper tubing or tape. They will cross the tubing sometimes, but there is a chemical reaction that takes place with their tender undersides and i usually find the slug a couple of feet away and very dead. It appears that most of the time they will not cross the tubing. Let me find a photo to show you how i use copper tubing. It is initially somewhat expensive but it lasts forever and with a small tool you can easily make your barriers to fit the space you want to most protect.
