How can I delete a "Single Time Slot" in Business Hours in my auto attendant without clearing all the hours of business I have configured already? As the only option is either Clear All Hour or Reset to default.
You can't. Options are you can only clear all hour or reset to default.
However what you can do is kind of merge two together. In other words where you had one covering a specific time, use two - for example, whereas I used one slot for Monday 08:00 - 18:00 previously I would now use Monday 08:00 - 14:00 and 15:00 - 18:00, so the slot is made use of without having to change anything else.
However, me being me I would probably take a screenshot, reset and re-do it then save the changes.
I think this should be a feature so I have raised the feedback item for you here:
When I first started using Teams Voice (2019), Microsoft did include a blank entry in the hours list for what appeared to be exactly this purpose. That is, I don't think it was a mistake that there was a blank entry included in the hours list.
Having to clear the whole slate just to set a blank entry for a single day is clearly a miss with Microsoft's process flow, so hopefully they can bring it back.
Sure it's a minor issue but it's minor changes like this that often end up causing the most frustrations with admins.