WSS FAQ how to remove or disable Windows Server & Windows Server Essential services

If you just bring up a new WSSE, the WSS2012R2 essential have setup wizard/dashboard to create AD server, thus you need skip and ignore this wizard and join AD manually as normal PC.

If you been configured the AD server already, please try on following link:

To remove a server role
https://technet.microsoft.com/en-us/library/cc782278(v=ws.10).aspx

Remove Active Directory Domain Services (Level 100)
https://technet.microsoft.com/en-us/library/hh472163.aspx

Removing a DNS Server
https://technet.microsoft.com/en-us/library/cc794727(v=ws.10).aspx

Remove Windows Server 2012 Essentials
https://www.dell.com/support/article/us/en/19/SLN283376/EN

Remove/Delete a Group Policy Object
https://technet.microsoft.com/en-us/library/cc770893.aspx

Once above link unable make WSSE remove the AD role, it is need restore WSSE to factory default:
WSS W2000/W4000/W5000/W2000+/W4000+/W5000+ how to recovery to factory default HDD content? (ALL HDD DATA WILL BE ERASE!!)
http://esupport.thecus.com/default_import/Knowledgebase/Article/View/269/0/wss-w2000w4000w5000w2000w4000w5000-how-to-recovery-to-factory-default-hdd-content-all-hdd-data-will-be-erase