You could create a page, then create an ACF group that appears only on this specific page, and then finally edit the WC checkout template to call upon these fields, using the page’s ID – get_field( ‘field_name’, $page_id ).
If creating a page for this purpose seems inelegant, you could use this plugin that allows you to use ACF on widgets:
Advanced Custom Fields: Widget
In your theme’s functions.php, register a new widget area for use on your checkout, then create an ACF group for this widget, insert it in and configure it. The plugin’s documentation has some specific instructions on how to call the fields on your template, but feel free to ask if you have any doubts.
