Put the cloned folder into the downloaded macOS Installer files folder (i.e.:
gibMacOS/macOS Downloads/publicrelease/xxx-xxxxx blah blah blah)
python3 <drag and drop PackAppMacOS.py here>
Choose the version you are installing.
The script should be packing your files to a Installer app. This may take time, be patient!
When it is done, proceed to next part.