How to create manually create my own ᴏᴛᴀ update file to be used for adb sideload?

In my case, I don’t want to permanently root my own device and if possible, I want to modify the /data partition directly. In order to do so, I want to add a single file to the /system partition or even apply capabilities on a single executable. That means no apk ; no new apps ; no bootloader changes. But everything I found for creating my own ota for rooting explains how to use adb to apply it, not how to build such a file myself. Or suppose that I’m building for a firmware I designed myself for which I have the signing keys (whereas the aim is to do it for stock Samsung). So **how to create my own file‑based** (with the aim to modify file permissions to existing files) **ota zip file which can be installed through adb sideload on all devices as SuperSu does** ?