EU BONELAB

-Happens somewhere at the end of every month, or beginning of the next one. You'll catch the announcement post for sure.
-Having your own content on your hard drive (say, avatars) won't let anyone else see it, and mod.io downloader seems to be flawed - usually one or more anons get left out with no content downloaded when another player uses something that's not a part of the modpack. And so, we use modpack content only,
-There will be two modpacks: Core mod pack, you're supposed to put that in <Game install folder>/Mods, and bigger content modpack that goes into AppData\LocalLow\Stress Level Zero\BONELAB\mods,
-You can use your own avatar, but you'll have to port it into Bonelab. It's relatively easy, aside of limited materials. Avatars are collected from the thread and put into a modpack,
-Modpacks are provided as a full package, so every time you see a new one, nuke your mod folders and replace them with new stuff.

BONELAB SETUP GUIDE

-Install MelonLoader, it's one click with basic automated installation, just select your Bonelab installation from dropdown list:
https://melonwiki.xyz/#/?id=automated-installation
-Once provided in thread, put both modpacks where they belong, so CoreMods into <Game install folder>/Mods, and ContentMods into AppData\LocalLow\Stress Level Zero\BONELAB\mods
-If you didn't play the game, you need a full save.

Game save

You need to progress through the game to unlock certain basic functionality, say, proper avatar selection with modded options. To avoid that, you can download a save:
https://mod.io/g/bonelab/m/100-save-file-patch-3
And put it in C:\Users\<user>\AppData\LocalLow\Stress Level Zero\BONELAB\Saves. Works just fine, according to anon who had this issue, but you have to remove all of the existing save files you had in folder and leave only new one in.

Other stuff

I've made my own mod/avatar/want to see a certain mod in pack

Drop it in thread! I'll find it and add it to the pack.

Minor avatar creation tips

In general, follow the guide on:
https://github.com/StressLevelZero/MarrowSDK/wiki/Avatars

But there's one thing that many were missing through the process: When you'll get Unity 2021.3.16f through Unity Hub, SELECT WINDOWS BUILD SUPPORT(IL2CPP) IN MODULES. Otherwise, you'll be getting an error somewhere along the lines of "Could not find a part of the path, somethingsomething/catalog.json", so if you have that problem, select Unity 2021.3.16f1 in Unity Hub, open "Add Modules", and add "Windows Build Support (IL2CPP)". Easy one to miss on.