Assuming you are using Sass, you can use either use font-url or asset-url to call your font. And considering you placed your custom fonts in app/assets/fonts, you should be able to call the fonts directly with no prefix in the path like so
@font-face {
  font-family: 'chicagoflfregular';
  src: font-url('chicagoflf-webfont.woff2') format('woff2'),
       font-url('chicagoflf-webfont.woff') format('woff');
  font-weight: normal;
  font-style: normal;
}
 
or
@font-face {
  font-family: 'chicagoflfregular';
  src: asset-url('chicagoflf-webfont.woff2') format('woff2'),
       asset-url('chicagoflf-webfont.woff') format('woff');
  font-weight: normal;
  font-style: normal;
}
or
If you are not using Sass, then with using url you should able to call the font with prefix assets not fonts like so
@font-face {
  font-family: 'chicagoflfregular';
  src: url('/assets/chicagoflf-webfont.woff2') format('woff2'),
       url('/assets/chicagoflf-webfont.woff') format('woff');
  font-weight: normal;
  font-style: normal;
}
And if you haven't pre-compiled your assets, your fonts won't appear. So you need to pre-compile the assets. For example for production environment do
RAILS_ENV=production bin/rails assets:precompile
and don't forget to restart the server