The best way is to have a star pattern with one central settlement where you dump all of your junk and materials. That way all other settlements can link to the one main base and have access to that junk. The snake system doesn't work because you're only getting access to the materials of the two settlements behind and ahead.
Without fast travel, you need at least two bases. One is Sanctuary of course for the beginning of the game, then you'll want a more central location so that you don't have to run back to Sanctuary every time you have junk to drop off. I use Hangman's Alley because it's very close to Diamond City and the center of the map. Yes it's a little crowded, but there is enough room as long as you build up.