$OEM$ Folders

To create a pre-activated Windows installation .iso, do the following:

Extract the $OEM$ folder to the desktop using the MAS script.
Copy the $OEM$ folder to the sources folder in the Windows installation media (.iso or USB).
The directory will appear like this: \sources\$OEM$ in your altered .iso or on your bootable USB drive.
Now use this .iso or bootable USB drive to install Windows, it will either already be activated (KMS38) as soon as it boots or will self-activate (HWID or Online KMS) at the first internet contact.
You can check here for activation method details and select the activation method as per your requirement.

warning

On Windows 8 and later, running setupcomplete.cmd is disabled if the default installed key for the edition is from the OEM channel, except for Enterprise editions and Windows Server operating systems.
However, in Windows 10, IoT Enterprise editions were not included in the Enterprise category list during the installation process. As a result, Enterprise with an OEM key can handle setupcomplete.cmd, but IoT Enterprise (LTSC) cannot. This was fixed in later Windows 11 versions.
In Windows 10 IoT Enterprise (LTSC), you can resolve this issue by using the Non-IoT Windows 10 Enterprise LTSC ISO. In this case, the HWID method in preactivation will install the IoT LTSC key to change the edition and enable HWID activation.
In Windows 11 IoT Enterprise (LTSC), it works fine as expected by default.

Edit ISO File

As stated above, you can copy the $OEM$ folder to your bootable USB so you don't have to edit the ISO file. However, if you need to, then follow the steps below.
Download AnyBurn Free Portable and extract this zip file
Run the file named AnyBurn(64-bit)\AnyBurn.exe
Select the option named Edit image file
Follow the on-screen instructions and add the $OEM$ folder to the sources folder so that the directory will appear like this: \sources\$OEM$
Save the ISO, that's it.

Windows Server Cor/Acor (No GUI) editions don't have the clipup.exe file.
To KMS38 activate it, you need to download the missing ClipUp.exe file from this link.
File: ClipUp.exe
SHA-256: 0d6e9f6bbd0321eda149658d96040cb4f79e0bd93ba60061f25b28fecbf4d4ef
This file has digital signatures that can be verified. You can also get this file from the official Windows Server 2016 x64 RTM ISO.
Put the ClipUp.exe beside the KMS38 Activation script. That would be either MAS_AIO.cmd or KMS38_Activation.cmd
The activation script will check ClipUp.exe in the current folder (from where script is running) and will use it accordingly.

When using HWID activation, no files are stored on the system, and Windows 10-11 will be activated when connected to the internet for the first time.

If Office is preinstalled then Ohook method will activate the Office immediately without Internet. This activation uses custom sppc.dll file for the activation.

When using KMS38 activation, no files are stored on the system, and Windows 10-11-Server becomes activated immediately without Internet.

When using Online KMS activation, Windows-Server and Office (Preinstalled) both will be activated when connected to the internet for the first time. This option uses a renewal task for lifetime activation.

In this method, Windows 10-11 will be activated with HWID, and Office (Preinstalled) will be activated using Ohook.

In this method, Windows 10-11 will be activated with HWID, and Office (Preinstalled) will be activated using Online KMS.

In this method, Windows 10-11-Server will be activated with KMS38, and Office (Preinstalled) will be activated using Ohook.

In this method, Windows 10-11-Server will be activated with KMS38, and Office (Preinstalled) will be activated using Online KMS.

In this method, Windows-Server will be activated with Online KMS, and Office (Preinstalled) will be activated using Ohook.