Addressing render-blocking resources in WordPress without using a plugin requires direct code changes, primarily in your theme's functions.php file and sometimes in your HTML header. It focuses on how the browser prioritizes loading JavaScript and CSS.

For a step-by-step implementation guide that includes the exact code snippets and detailed procedures for handling both JS deferral and Critical CSS extraction without relying on a plugin, I've covered the complete process in this guide:

How to eliminate render blocking resources in wordpress without plugin