This article explains how to capture the OS Partition through Windows Automated Installation Kit

This simple “Capture OS” feature works the best when you already have a OSRT as part of your Windows image. For example, C drive is OS partition and D drive is your recovery partition where the OSRT is sat. Then, connect an external flash drive to capture the OS partition into this flash drive. This usually takes only 1-2 hours.

The quickest way is to take out the internal storage loaded with the Win10 image. Then, follow these steps below to capture the OS image (w/all drivers and applications). Just ensure the WAIK tool you are going to install matches the OS version of your development PC. 

How to Capture the OS Partition through WAIK Tool:
1.    Please ensure you have installed Windows ADK on your development machine before you start
2.    Connect the source drive through a USB to SATA adapter to your development machine
3.    Click “Start” - “All Programs” - “Windows Kits” - “Windows ADK” - “Deployment and Imaging Tools”
*** don’t have to follow our naming rule in step 4.***
4.    Type imagex.exe /capture D: C:\Exxxxxx_Rev-X_XXX_XX.wim “Exxxxxx_Rev-X_OS” /Compress maximum

5.    Copy “Exxxxxx_Rev-X_XXX_XX.wim” image to an external storage device.

Windows version: Windows 10 LTSC
OSRT version: OSRT_P_10.0.17763-1809-P