It depends on whether you have attempted before or if your family/friends know you want to CTB.
The best way to make it look 'natural' is to be an addict or alcoholic. If you aren't one, it's very difficult.
I have reconciled myself to the fact that my family will know I CTBed no matter what I do, unless I pull off a Houdini or something. But if there is still a chance of you making your death look like an accident, recreational drugs, alcohol and accidents are your best shot.
These days, N is so hard to access that if you CTB with it the coroner and your family will know it was a suicide.
If only we were born 70 years ago when N and other barbiturates were still accessible. The government realized how tempting CTB was, and made N and other methods as difficult as possible to access to reduce CTB.