How do I make a custom Ubuntu ISO for fully offline installations?

I am based in India and we don't have reliable Internet everywhere. I would like to build an Ubuntu installer ISO with the following features:

• All proprietary drivers should be available offline


• At least one complete language pack (say, English/USA) should be available offline


• Certain extra packages


• And finally, things like flashinstaller or Chrome, which download data from the web while installing, should also work.

How do I go about building something like this?
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