The following guide is for who’s travelling and hunting treasures in The Witcher 3: Wild Hunt. You could find it particularly useful in case of encounters with Earth Elementals guarding those, like the one located North-East of Road to Bald Mountain. Each fight will require 8-12 minutes if you keep hitting them with no sli-ups, furthermore you can do it from about level 8.
This is what you will need:
Thunderbolt. It is optional but increases attack, so you’ll be better check if you have some on you before embarking on this journey
Roach. It will be better to have your loyal horse with you, best with Horse Blinders
Food. Earth Elemental is able to make severe damage during the combat, so you will need a lot of food in case you get hit.
At best you can take about 10 HP per hit, that’s not great. Most would rather walk away after a good 10-20-30 hits after seeing that they are making but, don’t worry, there is a simple method to defeating this thing. Call your horse, and get ready to mount and blade.
After studying the terrain, while on horseback, charge the EE and time your blade swings correctly. If you successfully hit the EE, it will almost always land a critical hit and you should inflict 250 - 350 damage to the monster (may be more or less depending on your sword and perks).
It ends up being easy is because the EE is very slow and generally stays in one small area.