I want to get into making my own recipes
Mastering Homebrew includes ideas, concepts, and processes for creating and understanding recipes. (+1 to
@Sammy86 for mentioning the book earlier). Currently, Mosher writes articles for Craft Beer and Brewing. Also, check out Mosher's web site for a free preview / sample of some of his books.
Beyond
How to Brew, 4e (+1 to
@hout17), Palmer has been writing articles recently for
Beer and Brewer (link).
Basic Brewing Radio (link) has been running a series on recipe development with multiple guests. Follow the guests to their web sites / videos / ...
Learn to understand flavor wheels (+1 to
@Bobby_M) for malts, hops, and yeast.
Hot steep method (link) can be used to explore a variety of malts side-by-side. Back in 2018-ish, my (now defunct) home brew club did this for a range of American and English crystal malts. Consider combining hop steep method with chewing on some kernels.
"Dry Hopped *** *****" (link) may be the "short and shoddy" "understanding hops" equivalent of Hop Steep Method. I did this once with a number of hops with different flavor wheels.
In addition to SMaSH (+1 to
@uweschmitt), with "constrained" recipe design, there is "brewing on the ones". And +1 to
@Protos for noting that "every ingredient should have a purpose".
BJCP and Brewers Association competition guidelines can be used to read about the differences between similar styles (e.g. American Amber vs Red IPA vs "Double Red"). Note that the BA competition guidelines are published every year.
I read a lot of good things about "Mean brews" (video channel); but have no first hand experience. There's also a "Perfectly Average" series somewhere (maybe
@VikeMan can help?)
Simple Homebrewing has a chapter on "simple recipe design" and offers recipe templates for a number of styles.
Josh Weikert's "Make Your Best ..." series at Craft Beer & Brewing.