Microsoft has just released the new Windows 10 build 14915 to the Fast Ring of the Windows Insider program. As you may know, Fast Ring releases are not available in ISO format, as they are made available via Windows Update.
Below we will see how you can create your own ISO for clean installations, from Windows Update files.
Follow these steps:
First, you will need to download the ESD files of Windows 10 build 14915. The direct links are below thanks to WzorNet:
Windows 10 build 14915 ESD files
Select a file that represents the version you want. For example, the file for Windows 10 build 14915 PRO x64 in English is:
14915.1000.160826-1902.rs_prerelease_CLIENTPRO_RET_x64fre_en-us_60c2ee424fc7c738745f6f0eeb1a6d2229637764.esd
Download the file to your computer.
Then download ESD Decrypter from the link below:
ESD Decrypter
Extract ESD Decrypter to any folder and place the ESD file inside the same folder.
Now right click on the decrypt.cmd file and run it as administrator. 
When the blue window opens, type 1 and press enter to begin creating the ISO.
Sit back and wait until the process is finished.
