Question

How to reate a block theme ?

Answer 1

Table of contents

1. Introduction.
2. Step 1: Create the theme folder and style.css. Minimum requirements. ...
3. Step 2: Add your first block template.
4. Step 3: Create the theme.json configuration file.
5. Step 4: Include functions.php and theme support (optional) Theme support.
6. Templates are loaded in the body element.

see link 

https://developer.wordpress.org/block-editor/how-to-guides/themes/create-block-theme/

Answer 2

this is an FSE theme