When using a custom Windows 10 1511 image captured with a SCCM 1511 client you might see that the step Setup Windows and Configuration manager will hang with the status Initializing the System Center Configuration manager client.
I you take a closer look at smsts.log you will see the message Waiting for CcmExec service to be fully operational.
According to Microsoft Connect this is a known bug and it will be fixed in the upcoming 16xx update.
Until then a workaround is to execute c:windowsccmccmrepair.exe right after Setup Windows and Configuration Manager step, and then add a reboot as shown here:
This can be done in the Build & Capture Task Sequence.