Adding Mailchimp subscribe into custom theme

I am creating custom theme and we would to add Mailchimp subscribe form. This is somewhat easy with Mailchimp for Wordpress plugin, but this plugin creates forms with certain ID and there is no possibility for us to pre-determine which form ID will this plugin create so when user installs the theme they will have to change form ID in the actual code and we would like to avoid this. So my question is how to create forms that can work with default theme installation requiring only adding Mailchimp api credentials (API key and List ID) into customizer.