How do you guys approach for free guest posting?

Do you need to act persuasive?
Or do you just write a casual email asking to guest post ?
I'd be glad if someone shared a guest posting email example template that worked for them.

Explain that what you're offering can be valuable to the person's website. Establish that you're interested in the same topic as him and you could potentially help each other. Start by offering your writing service for free. State that in the first line. Provide a few examples of the quality of your posts. Don't need to mention immediately that you're looking to link back to your site. Let him respond first, and only after a few messages ask him if it would be ok to introduce a backlink to your site.

Your emails should be convincing that includes factors beneficial on both sides.
Don't template the thing and reach many people.
Do some work or study on their site and reach, only if it is worth.
Also, check whether the blogger is active on most of the working hours.

Just found here the below thread,
https://www.blackhatworld.com/seo/getting-some-free-guest-posting-tips.1439055/
Test it whether it it works for you!

For free guest post you need 2 things
1 trust - use your real email , that would be I guess your Gmail. Another thing you need to do is get to their inbox. Going to spam automatically looses trust.
2 you need to offer something in return, could be money but since it's free you need to offer guest post on your other site(s) in return.