dwayne hi, here is custom CSS code:
/* Like+Reply label to Like+Reply fa icon button */
.item-like .Button-label { display: none;}
.item-like .Button:before {
font-family: 'Font Awesome 5 Free';
font-weight: 600;
font-size: 17px;
content: '\f164';
margin-right: 4px;
vertical-align: -1px;
}
.item-reply .Button--link:before {
font-family: 'Font Awesome 5 Free';
font-weight: 600;
font-size: 17px;
content: '\f3e5';
margin-right: 4px;
vertical-align: -1px;
}
.item-reply .Button--link .Button-label { display: none; }
.item-bookmark .Button--link .Button-label { display: none; }
.fa-bookmark:before { content: "\f02e"; font-weight: 600; }
Tested on: Flarum v1.2.1