This is a great question I've asked myself many times. I recommend:

- Rachel's English, both the [Youtube video](https://www.youtube.com/user/rachelsenglish/videos) as well as her [online course](https://rachelsenglish.com) - ELSA Speak, an iOS app that is great and whose pronunciation detection algorithm is uncannily good. The app design could be better, but it gets the job done and it makes me practice and learn what I'm doing wrong. However, I struggle to use it every day.

I'm open to finding new methods, but I generally find the available ones either too naive or too time consuming.