If I lived alone, my method would be Voluntary Stopping of Eating and Drinking (VSED). Most people die within 14 days. It may take only a week, or up to 21 days. You die from dehydration rather than starvation, though many people would become very thin in the process.
The more I think about it, the better this method sounds. There is time to mentally prepare to die. Many old people do it. I've read that some people have a really painful time of being so thirsty, while others experience it as a good and peaceful way to die.
I feel sad and regretful that I can't pursue this method (my mom would section me).