Reddit mentions of Accents of English I: An Introduction

Lexical sets like NORTH and FORCE come from Wells' 1982 book Accents of English, specifically the first volume. In the book, Wells proposes these lexical sets as a way group words that share a same phonological history. I don't have the book right in front of me so I can't quote it directly regarding NORTH and FORCE, but if you have access to the book through a library, that's probably the best place to go.

The instructions are definitely very interesting to read. Like, for RP ("Received Pronunciation," or standard British English), they tell you to articulate your words towards the front of your mouth, particularly the L sound. This can make all the difference - like with the word "skill," which can sound slightly more British depending on the area of the mouth you use to pronounce your L.

I've had the same issue with the Speech Accent Archive. It doesn't do very well in educating foreigners on the "usual" accents from each area. But it is rather interesting to listen to everyone, regardless. YouTube is definitely the best place right now to search for different accents, though watch out for the people who are just trying to imitate the accent and not actually from that particular region.

You also might be interested in this, which I've been recommended but haven't gotten around to reading just yet. It seems to be quite thorough, and approached in a linguistic manner, rather than "just" a guide for actors.