You boot to recovery and flash carbon. You then reboot to recovery and flash GApps. No further reboots or anything.
MicroG is an optional replacement for GApps. Neither are necessary, they are listed in the instructions as optional if the user desires to use either. No need to flash MicroG after GApps or at all.
Copy Partitions would be something you want to do before installing Carbon to ensure the stock rom is the same on both slots. Alternatively you could use stock, get the latest stock zip from XDA, then use Oxygens builtin updater to manually flash the latest zip, then reboot and do the same once more and you're ready.
See
this starting with step 10 on how to install a local update.
The reason reboots and all that stuff are required is because those will automatically switch your active slot. If you install an update, it will be installed to the inactive slot and the slot will be marked as active after a successful install. The reboot will then boot that newly installed update. In case of stock you'd then still want to update the old (now inactive) slot so you install the local update again, making you end up with the same version on both slots.
GApps however install to the currently active slot, which is why you need to reboot between ROM and GApps Install. Overall the process is as following:
- You are on slot A
- You install Carbon, to inactive slot B
- You reboot to recovery making you end up on slot B
- You now flash GApps to the currently active slot B
- You now have a full ROM + GApps setup on Slot B
- Profit.
Personally, I still use the "outdated" method of using the
Custom Recovery install, simply because that allows a flash and forget OTA survival feature which allows me to just upgrade through CarbonDelta and be done without extra steps.
For the "regular" and recommended install method, use a
payload extractor to get the boot.img from the flashable zip.
We are currently planning to automate uploading the boot/recovery images for recovery access as well as usage with Magisk in the future, probably alongside the release of our Android 12 builds to ease this up a little, but for now this is the way you have to go.
Both features are supported. You don't have to flash a different vendor image, but a different vendor_boot image whichs content previously was part of a boot.img but is now split between boot and vendor boot as part of the new GKI support. Those are needed to be flashed to get the custom recovery in which you can flash the ROM.
If you want to read more about that, check
Googles Documentation on vendor boot.