Blogspot or Blogger is one of the more established blog platform providing free hosting and domain (sub-domain with your-domain.blogspot.com) for all users.
And it's a secret to many that sitemap is actually generated automatically. What you need to do is to type out your URL and add sitemap.xml to it (example: http://your-domain.blogspot.com/sitemap.xml).
Below is the screenshot that your sitemap will look like:
