Yea sure friend you can ask me how to prepare for $OEM$ pack & it must be put inside sources directory of your iso where boot & install wim resides.
There are a bunch of scripts you can add to it .
$OEM$ directory structure must be like this :
$OEM$ then $$ = ( Disc drive Windows directory ) where $1 = ( Disk drive itself where you install OS )
now comes what to put inside these $$ & $1 directories,.
$$ - Setup - Scripts then there goes the firstlogon script named as "Setupcomplete.cmd" & the dependencies you are using inside your coding in this batch script. you can also call another scripts ie either bat ps1 cert etc etc via this.
$1 then any directory which contains files to be put at time of installation inside your OS for example if you want to put cleared live tiles layout template then the directory structure will be like this : first $OEM$ - $1 - Users - Default - AppData - Local - Microsoft - Windows - Shell - & here goes your edited defaultlayouts.xml for cleared live tiles on start menu.
you can add directories & files according to your Disk drive OS directories structure here in this $1 directory.
Pl feel free to discuss with me more about if you need any of your query resolved regarding the same query.