Guys, How are you even making these ai agents?

I've seen so many videos on YouTube may be 1/2 hour to 5 hour courses and none teach in depth about how to create your own agents. Btw I'm not asking about simple workflow ai agents as they are agents but not really practical. Are there any specific resources/Books/YouTube_videos/Course to learn more about building autonomous Ai agents? Please Help! 🙏🆘