How do you do inline association attribute overrides when your association doesnt match the factory name?

The docs here use the worst example where the association happens to match the factory:
https://github.com/thoughtbot/factory_bot/blob/main/GETTING_STARTED.md#overriding-attributes

factory :post do
  # ...
  author_last_name { "Writely" }
  author { association :author, last_name: author_last_name }
end

What if "author" is called "previous_author" on the model, I've tried every variation of explicitly specify the factory and it doesn't work.

eg: previous_author factory: :author { ... } doesn't work, previous_author { ... factory: :author } doesn't work etc. Is this just not possible?

Start with the overriding attributes section in GETTING_STARTED.md and reproduce the documented association example using a model attribute named previous_author and the :author factory. Check the existing documentation and tests for association overrides to determine the supported syntax. Done means the docs explain the correct form or clearly state that this case is unsupported.