actually the magloo trap design was given by the village chief right after you were given the quest. check the bottom most part of your trap synthesis page.. the magloo trap design is activated.
You need one Soul Stone (dropped by almost every monster on any map)
and also one Dog Soup (recipe is 2 Dog Meats or you may choose to buy at the night store at Eirene)
you may need to synthesize about 20 pieces of magloo traps or just try to make about 30 to make sure you have enough.
after making enough traps, set the hot key for the magloo traps.
setting the magloo traps on the map seemed tricky for me at first try but then I realized that you just have to stand on top of the holes (I repeat, ON TOP of the HOLES and not beside. don't calculate how far from the hole you'll stand to set the trap on the right place. you just have to stand on top of the hole and hit the hotkey for magloo trap)
if you have successfully set the trap on the hole, the trap would immediately cover the hole and the hole would disappear from the map.
do this to all of the holes while killing as much snakes as you can before more of them come out from the holes. when all of the holes have disappeared, then no more snakes would appear and just kill those that are present.
quest completed