There are, at least, 2 ways to do this.
You need to group 3 (or more) enemies. Either by luring them to an area by throwing something or have them chase you. Then you need to either:
1) Throw a Water Jar at their feet. Followed by a Shocker to electrocute them
or 2) Throw a Rubber Explosive near them.
I found it easier to do this an area where there were at least 3 enemies walking around and there was something to climb on. Run around and get 3 (or more) of them to chase you. Then climb up onto the climbable object. Use either of the methods mentioned above. The Rubber Explosive is the best option (if you have it) Especially if you also have the Harper Upgrade (Explosive Radius)