You didn’t answer to the question but that’s ok. I’m working for a client who chose your theme, I’ve implemented the child theme manually for custom code and I’m used to do it. But to do things correctly, and the WordPress docs link you gave me mentions it too in “3. Enqueue stylesheet”, the content of functions.php in child theme depends on how the parent theme works.
The only thing I was asking here is the minimal content of style.css and functions.php in child theme when you implement it manually with Freshio.