I'm looking forward to giving it a go.
I second Hangman's Alley. It's a central location that is very enclosed and comes with its own pre-built walls. It only has a weapon bench and cooking station, but Diamond City is only just down the road to suit your armor crafting and trading needs.
A certain fort which is part of a quest. Lots of water around it so it makes for a good place to farm purified water.
There was another one which I accidently stumbled across on a previous game that had lots of ground to farm and a good location near water and was fairly defensible. I just wish I had paid attention to what it was named and where it was because now that I am actually building up settlements in this game I really want to find it.
I have seen people on other forums suggest Starlight but I don't find it that great. Very little ground for farming and its on the outside edges so you have to walk a bit to collect crops. It only has one spot for getting water and its far enough away that you have to spread out your defenses more.
I'm not a big fan of hangman's. You cannot clear out that annoying little nothing of a shack. While you can build up, up and up, there is no water source, so your pumps compete for dirt with crops. Now, if you don't care about population, and you do not unchain the one door, it is reasonably defensible, yes. But listening to gunfire from nearby conflicts makes it hard for me to sleep.
Exactly the issue for those who didn't happen to invest in Charisma, or Local Leader for that matter. But as I said, the convenience of Diamond City negates some of these issues for those who don't have the perk.
Definitely not the best place to build a full on settlement. But for someone who would prefer to live alone? I'd say its the perfect confined spot. Even then though, I've seen a lot of crazy things people have done to make it a successful settlement.
I'd say its only flaw for me is the pre-built shack that can't be removed. Why it's like that, I will never understand.
My favourite settlement is the island.. a whole flipping island to craft. That's Bethesda's way of saying "you've completed the game, now go off and go full-on Minecraft" lol