Make sure as you’ve been progressing that you’ve collected the red moss and put all of your efforts into gaining the water jar and the electro bomb as soon as possible as these will be required to kill 3 enemies at once.
The first and easiest opportunity you’ll probably get is shortly after leaving the caves and entering a military looking research post. After you’ve worked your way through over a couple of electrocutable fences you’ll come to a split area where the path can go either left of right but will rejoin at the opposite end with a crate waiting to be moved in front of a fence.
Be cautious first and sneak to the other side and move the crate into its place so it becomes climable. Now, take a sprinting lap of the area and gather up the guards and get the to chase you to the crate. Climb up and with your torch on for added effect they should gather round unable to get you.
Turn off the torch and try to throw a water jar as close as you can (you can’t aim low enough to hit them). They should hear the smash and investigate the noise. I threw another jar to make sure followed by the electro bomb, actually netting me 4 kills in one!