json – How to deploy chromium from source with the master_preferences?

I have tried following this Bundle a file in Chromium but the file was not present alongside the .exe after the installation, it was added in the version directory. I also read this Where do I put the master_preferences file for a Chromium build on Windows? but it wasn’t clear about which C++ files I need to edit.

I want to make a mini_installer.exe which creates a master_preferences file in the same folder as the .exe file. I am basically trying to open the welcome page on the first run by the user.