You could create page templates within the theme. So, for example, for your About page:
- Create a “page-about.php” file in your theme
- Include the content there, but instead of using
requireuse the normal WP functions (i.e.wp_head()) so all your plugins’ scripts and styles will load properly - Create a Page in wp-admin with the slug “about”. You’ll want to include a title (About) but you don’t need to include anything else there, unless you want to put a little reminder in the main content editing area “The contents of this page are controlled by the theme” so if anyone looks later they’ll realize content pasted here will never show up on the page
This will give you actual Pages in WP, which not only enables pretty permalinks (/about/) like you’re asking for, but also other functionality – like sitemap generators including these “static” pages. You may eventually find it might be easier to manage these pages’ content in wp-admin itself, in which case you can simply remove your custom template (page-about.php) and paste your content into the main editor.