Can you tell us what is the best way to get a natural backlink to your website?

Natural links can not be built, it is generated automatically by others who find your content useful.

Leverage public relations.
Write competitive content.
Do an original study.
Create an infographic.
Write testimonials for other websites.
Link externally and then reach out.
Comment on other relevant blog posts.
Align social signals.

you can get natural back-link for your website is "guest post"