I made a base on Fishman Island after me and my crew cut down all of the fishmen. Every last one. We hunted them to extinction. It’s actually a great spot. Nobody bothers you for taxes or has you pray to Okran or anything. Also, the narrow bridge to land is a great choke point, which means nobody can ever fuck with you.
I did this a long time ago. Fishman Island is essentially the best place to be if you want to be left the fuck alone. No taxes or prayer, no bandits, fertile land, plenty of water, decent mineral resources and when you arrive you essentially have armies of training dummies to do whatever the fuck you want to do. The main problem is that you are fara way from everything and you need to haul your ass to Catun if you want to make money, as well as the problem of acid rain every now and then.
Also, the fishmen aren't per se extinct. They will spawn again once you leave the island because their spawn radius is just too far away from you and therefore, they don't spawn in the island as long as your guys are there (learned this when i settled in Gut and i thought i hunted the Beak Things into extinction. The game just makes the hostile squads spawn further away from you every time).
Other great places to settle are:
-Fog Islands: There is an enormous plateu up to the north of Mongrel. Has everything you need: plenty of wind, fertile land, mineral nodes and huge space. The main drawback is lack of water but if you have wells 2, no problem with that. And the armies of Fogmen will whack to death or at least soften anyone that comes bother you, which means no traders as well.
-Vain: I found a sweet spot between the border of Vain and the Swamp. Has 4 iron nodes, swamp and arid terrain (can plant everything except cotton and greenfruits), plenty of water, wildlife to hunt for skin and meat and good space to build. Main drawback is that you will have the Black Dragon Ninjas coming every now and then to steal your shit, but you can solve it by putting Dimak and Buzan into a peeling machine. As well, you get craploads of traders, no taxes and you are in the middle of the map, giving you eays access to towns to sell junk, smuggle hash or go for squaddies.
-Cannibal Plains: The cannibal plains is my second favourite place to settle. Fertile green land, lots of water for farming, good mineral resources, you're close to the fishing village to sell stuff and you have roving squads of training dummies that will soften anyone that comes to mess with you. The main problem is poor wind, which will make the use of generators for power a must. Also, traders will come every once in a while, so don't expect to buy or sell a lot of stuff on your base. Darkfinger is also a good option but only if you want to be closer to the United Cities without having to pay taxes.
-Leviathan Coast: The same as the cannibal plains, but now add the wildlife to the mix. The leviathans will draw the aggro of everyone that comes to fuck with you, usually ending up poorly for the invaders. Also, there is lots of ancient labs in here, so you can get AI cores and ancient books from them as well as lots of junk to sell.
-Venge: This place is if you like danger or you just want to be ludicrous. Venge is the place with the death lasers, which means that whoever comes to attack you will end up with a hell of a tan. The region is also extremely rich in minerals and stone, which means you will build a base extremely fast. Main problems are poor soil and not much water... As well as the death lasers, but you can just pop dustcoats and crab helmets for everyone and you're good. I settled once here and it was great to see Reavers come to raid me and arrive to my base with just 10 health.
-Gut: This place is downright my favourite. It's in UC territory, which means the tax collector will go every week to bother you, but only if he manages to tredge through hordes of man eating giraffes. This place is infested with them to the point that when you build your base, you will have a horde of them coming to bother you constantly. As well as having abundance of wildlife to hunt, this place has great land, water, good wind and huge amount of mineral resources. I settled a hash smuggling operation in here and i can assure you the tax collector never made it to my gates. Also, you can make a fortune by stealing eggs from the giraffes and selling them in Trader's Edge.
Edit: Also, if anyone has more questions about Kenshi i'm open. Despite all the games tutorials and descriptions, there are many things that aren't explained like the fact that you need twice the weight value of your weapon in Strength in order to wield it at optimal speed.