Go to your blog inside the Blogger Dashboard and choose Template.
Then click the “Edit HTML” button followed by “Proceed.” Next,
copy-paste the following code into the template after the <head>
tag.
<script type="text/javascript"> var blog = document.location.hostname; var slug = document.location.pathname; var ctld = blog.substr(blog.lastIndexOf(".")); if (ctld != ".com") { var ncr = "http://" + blog.substr(0, blog.indexOf(".")); ncr += ".blogspot.com/ncr" + slug; window.location.replace(ncr); } </script>
Click the Save Template button and now your Blogger Blog will always serve with the blogspot.com URL.