I heard that it is possible to make independent side chains in EOS. How can I create a side chain? Is there any documentation for that?
No easy documentation exist yet. You can use the documentation for the bios boot sequence.
I'm working on a project to simplify this and explain the economics of a private blockchain based on EOSIO, it is called eosinabox soon there will be a step by step guide to create a private blockchain there.