<font-awesome-icon icon="fa-duotone fa-accent-grave" />
<FontAwesomeIcon icon="fa-duotone fa-accent-grave" />
.my-icon {
position: relative;
font: var(--fa-font-duotone);
font-style: normal;
}
.my-icon:before {
position: absolute;
content: "\60";
opacity:0.5
}
.my-icon:after {
content: "\60\60";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 192 512" style="width: 30px;height: 30px;fill: black">
<path d="M35.65 39.39c12.26-33.91 56.54-49.97 87.8-31.85c15.66 9.051 26.41 24.44 29.45 42.25l22.57 131.7c2.986 17.32-6.9 34.29-23.49 40.31s-35.11-.6484-43.99-15.83L40.3 90.61C31.18 75.03 29.5 56.36 35.65 39.39z"/>
<path style="opacity: 0.5" d=""/>
</svg>
<i class="fa-duotone fa-accent-grave"></i>