Microsoft has published the final version of Windows 10 1511, known as November Update/Threshold 2 for free download. Now you can download official ISO images to perform a clean install of Windows 10 1511 RTM.
There you can pick the desired edition and download the ISO image directly.
Windows 10 Media Creation Tool
Windows 10 Media Creation Tool is a free tool released by Microsoft. It can also be used to download the ISO images of Windows 10 and create a bootable USB flash drive.
Important note: If you have a genuine previous version of Windows like Windows 7 and Windows 8/8.1, you can enter its key during the clean install of Windows 10. Windows 10 November Update 1511 accepts keys from previous versions of Windows.