Girdle the pot with adhesive copper tape. You can buy rolls of it on Amazon: just clean the sruface with alcohol beforehand and you are good to go.
There's a never ending debate on why snails won't cross copper-covered surfaces but they surely don't like them and that's enough for me.
Copper covered lengths of PVC tubing is what has allowed me to grow eggplants once again and girdling the containers I planted Hippeastrum in is what saved them from being devoured into oblivion.
