Back in 1960, U.S. Army Captain Bertrand Brinley published the Rocket Manual for Amateurs, one of the greatest DIY books ever written. Its cover price reads 75 cents. Buying a copy today in a used bookstore could set you back more than $100. But it's that good. (I know, I have it.)
There is a considerable amount of information on rocket motor making in RMFA. The line drawings are excellent and the writing clear and straightforward. A lot of people bought this book back in the 50s and 60s, because making rocket motors was a fashionable pastime, and there were lots of clubs and societies that would tinker around making rocket engines.
But like any high energy hobby, things could and would go wrong and people got hurt. Rocket engines had a nasty habit of blowing up in the maker's face and causing injury. There is a part of the process where the propellant is rammed into a tube and that's pretty dangerous. (I personally know of a couple people who hurt themselves this way.) So, the activity changed, and rocket people were encouraged to buy commercial rocket motors instead of rolling their own.
That is indeed much safer. But I think you lose something when you give up the core part of the activity. That's why in Absinthe and Flamethrowers I provide instructions for creating a small but powerful rocket motor wholly out of stuff available at Home Depot or SuperTarget. There's just something so ... satisfying about homebrewing a rocket with stuff you got at Walmart.
Brinley's book contains instructions for making for "micrograin" rocket engines (pulverized zinc and sulfur ramrodded into a steel container.) I tried it and it burns like crazy. Whoa nelly, that's some hot stuff. Probably too dangerous for an amateur.