Line 10 in a half circle. Put stone in inventory so they can't move. Put dino leash down on lowest setting, just incase. They are very good escape artist. Place gacha down and let gacha pick up all the paste. Getting 200 stacks a day. Better than farming. Only upgrade weight in gacha and food in snails.
When tamed, the Achatina can produce Achatina paste, an alternative to cementing paste, passively when on wandering. You could also collect it when they are moving, their paste/slime will be on the ground shaped in a similar feces ball.