If you don't own any of the extra content or toys, this is the easiest way to knock this out.
TLDR:
Start a new game on easy and head to Araki Village. Use the Stasis Canister there on the enemies, then hit them with the Flamethrower.
Full Explanation:
Start a new game on easy, and equip the Flamethrower. Play through the tutorial until you crash onto the planet. Fly forward and take out the enemies to reach the Equinox. The game will have you open your map. Let the dialogue play out then close the map. Once Levi talks (he mentions "killer robots") pause and quit to title. Load your game back up and you'll be in a very specific spot. Only using

, aim at the Equinox, then open your map. Pan up for about three seconds, then right for one second. This is the approximate location of Araki Village. On the way there you'll pass the monument on your right and a crashed Drake on your left. When you get there fly around and get their attention. Make sure they're all shooting at you. On the map look for the blue chest. Head around the right corner of the building to find the Cold Cashe. Go behind it into the little alcove. Hang out until they all bunch up trying to get to you, then hop up onto the ledge on your right. Follow the path to the right and you'll find a Gravity Canister and past that a Stasis Canister. Grab the Stasis and hop back down. Fire it into the middle of the pack to raise them into the air, then hit one nearest the middle with your Flamethrower. The explosion should hit at least 6-7 of them.
If for some reason you don't get it to pop, just quit, reload, and head back to Araki Village. The enemies and the Stasis Canister respawns so you can try it again.
I based this guide off BipedFungus484's guide and Retrologue's comment. Works like a charm.