As A Biron mentioned, after you've verified that the
noindex directive is properly written, use Search Console's coverage tool to look at the number of "valid" indexed pages.
If there are still results, either wait for Google to re-crawl your site on its own, or use Search Console's temporary removals tool to pwn your site's entire search presence at once.
You'll need to verify your site with Google Search Console to be able to use this tool.
I'm not about to try it on my own site, but I bet if you put your homepage url into that box and click "remove all with prefix", Google will deindex your entire site within a day or so.
Double-check your work by going back to the Search Console coverage tool to make sure there are zero "valid" pages, and use the
site:example.com query with your domain in Google Search to make sure there's nothing there either.