Best AFK spot?

So a you might know lately I have been doing research about the ideal standing point for my mob farms. I already know the simple 24 block or farther thing for them to move 128 blocks despawning and not moving stuff but I still do not understand most of it.

For example if I built a slime farm from bedrock to y=34 using iron golems where exactly should I stand? I already made an afk platform at y=91 and afked it for about 10 minutes and came back to nothing at all.

Another time, I was just crafting some pistons at my crafting station about 40 blocks away from the farthest point of one of the spawning platforms and came back to whole 12 slime balls.

So does the 24 block rule mean 24 blocks away from the chunk or from the spawning platform or something? I am having a lot of trouble finding out exactly where to stand for ideal performance of my farm. And yea I am on a Spigot community server with about 2-4 people online normally, but this morning I was the only person online, if that affects anything.