I am using Font Awesome and do not wish to add CSS with HTTP. I downloaded Font Awesome and included it in my code, yet Font Awesome is showing a bordered square box instead
Watch out for Bootstrap! Bootstrap will override .fa classes. If you're bringing in both packages separately thinking "I'll use Bootstrap for responsive block handling and Font-Awesome for icons", you need to address the .fa classes inside Bootstrap so they don't interfere with Font-Awesome's stand-alone implementation.
eg: font-family 'FontAwesome' in Bootstrap will interfere with font-family 'Font Awesome 5 Free' in Font-Awesome and you will get a white box instead of the icon you want.
There may be cleaner ways of handling this, but if you've gone down the checklist trying to fix the "white box" issue and still can't figure it out (like I did), this may be the answer you're looking for.