When the server was created did you guys happen to turn off slime chunk generation? I use FTB/Curse to launch my modpacks, this pack base does not come with a minimap, so I added Rei's Minimap just so I can see if slime chunks existed or not. With grid + slime chunk enabled in the options, slime chunks would appear in a red chunk within the grid on the map. Oddly enough with a few /rt commands in the overworld and farmworld I cannot see any slime chunks. I tested a newly created single player world and I did find slime chunks right away from the spawning location. In short, trying to find out the way method to get slimeballs and so far it might have to be a swamp which is not as easy to create a farm for.
Slime chunks won't show if you don't know the world seed. Other packs have server side mods that send that information to you.
Thanks, I oddly found a slime chunk nearby my base and already started to do the clearing for the farm. I also found an oddity of an abandoned mine which has a low point of y=2 any lower it would and could of broke through into the void lol.