Best way is with a paracer and cannon on top. Find a mountain cliff side and place 2 high pillars in a semi circle, 8 pillars should do. Leave one side open. Agro the Elemental with a bird preferably so he doesn't throw rocks. Once he walks into the trap, sprint away from his targeting range. This will cause him to De-agro and go back into a disguise. Keep your distance when returning to it. Go to the side that you left open, with pillars in hand, and sprint in to place the 2 tall pillars as fast as possible. (Dino Gates work as well) I would recommend have a sleeping bag or bed nearby. Now comes the tricky part, find a rock or structure to hide behind that is near him, get his attention and wait for him to just stop moving and stare at you. (You need to be on foot) If he does this, back away and he will stay like that. If not, Get close to get his attention and repeat. Now simply aim and fire. 20 balls for a 120. You must hit it in the head and it must do a dramatic flinch.
To tame these turret soakers I’d recommend getting four metal gates 5 pillars 3 ceilings and 3 walls. For the trap and the pillars are supposed to prevent the golems rocks from hitting the cannon. AIM FOR THE HEAD
For some reason, after the latest update, X-rock elementals (haven't checked other variants) are no longer tameable. Whenever you knock them out, they don't eat and don't have a taming bar. Forcetame also doesn't affect them, so I believe it's a glitch