Some public libraries have digital collections that could include BL stories that you can access for free. Also, some authors might offer free samples or short stories on their personal blogs or websites.
Honestly, I don't have a definite answer for you. It's not recommended to look for free reading sources that might violate copyright laws. It's better to support the creators by using legal paid platforms.
You could try looking on some fan-run forums or blogs dedicated to BL manga. But keep in mind that not all of the content might be authorized and could have copyright issues.
Well, finding free and legal BL manga can be quite tricky. Sometimes, some libraries offer digital access to a limited selection. But please note that most unauthorized free sites are against the law and might have risks like viruses or poor translations.