What additional configuration is required? I was under the impression it couldn't be blocked at all due to ads being served from YouTube.com domain or similar.
Would really like to implement it on my own PiHole
Let me offer an alternative answer to tubularhells' unhelpful answer:
There isn't really a good, efficient easy way to block YouTube ads with Pi-Hole. It's a constant cat-and-mouse game of finding the appropriate domain regexes and keeping them updated.
Would really like to implement it on my own PiHole