At the beginning of the year I had a go at designing low content books to be sold via Amazon KDP.
How it works: You design a cover and interior of a book like a notebook or planner, upload it through Amazon KDP and it gets listed on Amazon and people can buy it. The books are printed to order by Amazon. After designing the rest is left to Amazon though you may want to advertise your book and share it on socials to get noticed as it's a very saturated market and it's hard to get your books seen. You choose how much profit from each book you get by setting the price. You can also buy the books yourself at cost if you wish to sell them yourself through other means.