Please have mercy on a dumb novice and give me guidance on this simple usage case (Chrome + built-in mic --> Another app)

[seouled-out]

I'm using an app called Clubdeck to join others in a live audio discussion wherein we play, listen to and discuss historical speeches. When I play speeches for others, I use Google Chrome to play clips from YouTube and Otter.ai. The sound comes out through my Mac speakers, and then the audio comes back in through the built-in mic, so it's of course degraded.

I want to somehow combine Google Chrome + the built-in Macbook Air microphone into one thing — I believe an aggregate device but I could be wrong — and then choose that as the input within Clubdeck.

I then want to choose my bluetooth earbuds as the audio output within Clubdeck.

Here is what I'm trying to do.

I have read instructions in the wiki for "aggregate device" but it is really confusing to me, the descriptions are ambiguous and clearly not intended for anyone new to digital audio, and in some cases the images do not match the specific instructions. Also, it says the built-in speakers must be included on the aggregate device....? I don't want anything to play out of my speakers, because I don't want my mic to pick that up!

I have attempted to follow the instructions on https://existential.audio/blackhole/support/ to "Route Mic and System Audio" but honestly I'm not even sure if that describes what I am trying to do.

Would anyone please please help me out