Yup. Common question. What have you tried so far? Remember that you need both halves: the redirect to change the URL displayed in the user's browser, and then a rewrite to fetch the content from wherever it "really" lives.
You've been around since 2006, so you know nobody is going to write it out for you.
But before you start...
The thread title says "removing html". Going extensionless is popular. But the content of your post says something slightly different: Now you're talking about redirecting from the requested filename, like
to a pseudo-directory
as if each individual post lived in a directory of its own:
It isn't flat-out wrong, but it seems unnecessary. Before you start laying out your rules, make sure you've settled on the official form of your page name.