FM synthesis really isn't that hard, there just aren't a lot of general tutorials on how to use it. I skip over the basic premise of FM and instead touch on FM theory and how you can use that theoretical knowledge to start designing sounds with FM, without feeling like you're changing parameters at random.
0:00 Intro
3:29 Part 1: Brief overview of FM theory
8:16 Part 2: Understanding the 2-op structure
13:57 Part 3: Understanding feedback
23:08 Part 4: Approaching algorithms
34:42 Part 5: Algorithms in action
52:29 Tips & tidbits: making a triangle wave
55:57 Tips & tidbits: non-sine waves
59:40 Tips & tidbits: synth recommendations
1:06:42 Outro