Need to Setup Public Unsecured Share

Might sound like a dumb question but I can't seem to figure it out...

I need to setup a completely open file share on a Windows 2012 Essential server. For an access 2010 database file sharing so that XP (OS)users can use the database files for POA cash registers.

In other word a place where anyone connected to the LAN can read / write / delete files (within the assigned storage quota). No question ask, no password, completely open, for anyone on the LAN, even for machines not joined to the domain or non WinTel OS (Mac or Linux clients).

Thanks in advance for any pointer / suggestion