Register post meta using the register_post_meta() function hooked to the init action early in WordPress’s bootstrap process. Specify the post type, meta key, and configuration arguments for proper integration.
Key arguments include type (string, number, etc.), single (prevents duplicate keys), show_in_rest (enables REST API access), sanitize_callback (security function), and default (fallback value).
Use prefixed meta keys to avoid conflicts with other themes and plugins. Set single to true for most use cases and always include a default value to ensure block binding interfaces work properly.
Register separately for each post type that needs the meta field. You can register multiple fields in a single function by calling register_post_meta() multiple times within your callback.