This rarely happens. The Berkley Open Submission Program (Penguin/Random House, one of the big publishing houses) is allowing writers to submit a ten-page sample of their completed manuscript, NO AGENT NEEDED. "We’re looking for commercial and genre fiction in the following areas: romance, women’s fiction, contemporary fiction, historical fiction, mystery/thriller, science fiction, fantasy, and horror."
Here's the link. It's a REALLY short submission window: Dec 7th, 2021 - Jan 9th, 2022
https://sites.prh.com/berkley-open-submission-program
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Submissions must include a 1-page synopsis, the first 10 pages of the manuscript, an author bio, and a query letter with links to social media platforms, if applicable, and any other information you wish the editors to consider. A query letter is an introductory one page letter that tells an editor something about the story, something about the writer, and why Berkley should publish the book.