Second best is to do it without the support and discipline of a teacher. It's just like any other thing that takes skill. You can either stand on the shoulders of giants and learn from their wisdom, or you can go it alone and make the mistakes and form the bad habits they could have warned you about. And when it comes to a musical instrument, it's all about the FEEL and POSTURE as you play, which only in-person teachers can show you.
Anyone can take a hammer and saw and build something that resembles a table, but the one who learned from a craftsman (even for just a little while) will be able to produce far better work with far less effort and mistakes. Knowing how to draft and read plans will also go a LONG way towards getting good results.