Why font awesome icon shows empty squares?

Question

I would like to make a combination of icons via FA stack but it does not work. I have pure example from documentation and it shows me only empty squares. Code looks like:

<

Answer 1

Use the correct CDN which is the one of the V5 not the V4

<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.12.0/css/all.css">

<span class="fa-stack" style="vertical-align: top;">
    <i class="far fa-circle fa-stack-2x"></i>
    <i class="fas fa-flag fa-stack-1x"></i>
</span>