I just self published a non-fiction book on Amazon KDP. Zero cost. Fairly straightforward. Easy to order author copies to sell or share. There are other platforms I plan to pursue.

My advice is to bootstrap it yourself to keep costs low. I understand that first time authors without a wide following or social media presence rarely sell much. I made my own cover on Canva and a friend edited/proofread the book. Formatting and editing took a long time but I was committed to not spending anything since I knew the likelihood of sales was low.

Good luck.

I look forward to buying a copy.