You don't need to switch slots manually, generally ever, when updating your phone. If you flash full factory image, it'll just install over your current active slot and done. If you sideload OTA zip, it'll flash to the other slot and change slots for you and boot (you won't even notice it happening tbh).My Pixel 7 is the first phone I've run rooted since my OnePlus 6T on Android 9. It appears the process to OTA update has changed since the last time I did it a few years ago. If I follow the steps in post #2 of this thread to update (running modified flash-all.bat w/ full factory image, patching the init_boot.img in Magisk, flashing patched .img), will this automatically put the new images on the inactive slot then switch it to active? Or do I need to manually switch slots first then run flash-all.bat?
One question though: are you currently running with verity/verification disabled? If you don't know what I'm talking about, it's probably a "no", but keep in mind if you want to flash a custom kernel for this device you'll need to disable them. And unfortunately that will require a data wipe the first time you do it, and then you need to remember to disable again each time you update on future updates. There's a very slim chance they'll find a workaround to needing them disabled eventually but I wouldn't count on it. More info on this can be found in the OP's and kernel development threads (e.g. Kirisakura). If you don't care about flashing custom kernels, simply disregard this last point and the next.
But my major reason for that last point is that if you are running verity and verification disabled, in that case you may want to manually switch slots and flash full factory image with v/v disabled as a means of being overcautious. My reasoning for this is that you never know when you may run into a bootloop from a bad flash, which will automatically trigger an active slot switch, and once it attempts to boot without those flags disabled, you're beat and have to wipe. So out of an abundance of caution, I flashed both slots last month with the flags disabled.