In the FLEDGE MD - https://github.com/WICG/turtledove/blob/main/FLEDGE.md it says that the Publisher can also create interest groups:

A publisher (or a third party working on the publisher's behalf) might create and own an interest group of people who have read a certain type of content on their site. Publishers can already use first-party data to let advertisers target their readers on the publisher site. A publisher-owned interest group could let publishers do the same even when those people are browsing other sites. Publishers would presumably charge for the ability to target this list.

How does the auction work, more specifically how would the buyer bid for this audience?

My understanding is as follows:

1. When a user lands on the Publisher website, the Publisher executes joinInterestGroup.
2. Publisher / Seller somehow informs the buyers that there is this interest group that they could bid on. Not entirely sure how this piece works.
3. The Publisher / Seller initiates runAdAuction.
4. Authorised buyers will need to have added the interest group and keys to their KV server.

Questions:

1. Since the interest group contains information such as renderUrl etc ... that can only come from the buyer how would the Publisher create the interest group?
2. How does the buyer know what interest groups to add the KV server?

My question is unltimately how would a buyer bid on an interest group that is created by the publisher?

Thanks