The easiest way is to wait for a Faction Assualt in Nazmir with the quest at the dock with the azerite flare available(Also helps if it also the CTA that week too)
Go there and complete 4 of the quest, but not the one at the dock.
kill ten horde to get your assassins buff and N’zoth quest. But don’t kill any horde in the dock quest area. Otherwise you might not be able to pick up the flare if you kill to many completing the quest.
Now grab the Azerite flare and wait near submarine for alliance to be finishing the submarine quest. Blaze away as the appear. You can pick up the berserker buff that’s near by to make kills even quicker. You can also fly up and down the dock area for alliance kills, but you want to void killing any horde, or horde NPCs if possible. So its best just to stay near the Submarine and get kills there. You can also use the Submarine to escape if you’re going to get killed. But remember not to do any damge to the Submarine, or it will turn hostile and you won’t be able to use it(got screwed over by that happening because of AoE damage, thankfully I had other means of escape). Hopefully you can get enough kills before getting a bounty put on you.
This is how I obtained mine solo.