What are some ways to publish a book for free? Is it possible to self-publish a book without assistance?

Yes it is possible - check out Amazon’s Kindle Direct Publishing (KDP).

KDP allows you to publish a book without any upfront costs. They print on demand, so you do not have to pay upfront printing costs.

KDP gets its money by taking a portion of the sale price. With printed copies, this is after printing costs. This means you do not get all of the sales money—however, Amazon also takes care of the shipping, etc., making selling your book really easy.

One thing to be aware of is that you will need to promote your book yourself. You can do this at no cost if you have a social media audience or your book pertains to a particular industry; see if the industry publications will promote it. You are unlikely to get sales if you print it and do nothing to encourage sales.

You can pay someone to edit your book or design your cover, but if you do this yourself, you avoid these costs. I would, however, recommend finding someone you know to proofread it before publishing it. It isn't easy to proofread your work correctly, but it will make a big difference in the quality.

Platforms such as KDP publishing make it accessible to publish a book - so if you want to do it there is nothing stopping you.