You can love them or hate them but personally I think their fun. On the slime chance that you don’t know, the idea of a Character Funnels comes from Dungeon Crawl Classics. The players each make a bunch of 0-Level characters and hope somebody survives.
So let’s make this super simple. Roll your stats. 3d6 in order. Good luck. Characters have 1d6 HP. Saving Throw 15. And 10 GP of equipment. (Trust me look at WBFMAG equipment list. That ain’t much.) OK. Then pick some sort of mundane occupation with the GM’s approval. I’d say roll up about three or four characters.
Now here’s an extra stop that I think is helpful for the GM. The player picks the potential class of each of their 0-Level nobodies. The point for this is so the GM may add things that would make sense for a character to gain that precious class level. So relevant treasure (like perhaps an ancient spell book for Magic-Users; a holy symbol for a Cleric, maybe a nice sword for the fighter, or maybe a lost letter of introduction to the local Thieves Guild.) See you get the idea.
Now it’s off to adventure and hope some characters survive! So what happens if somebody has multiple characters survive? Congrats. You start off with hirelings.
And there you go. Have fun rolling those dice!