JSFiddle - React, Tailwind, and code Playground

HTML

<div>
<div class="wrapper inner">
    <div class="abc"></div>
    
</div>
</div>
</div>

CSS

.inner{position:fixed;}


.border{width:72px;height:52px;z-index:-1;top:0px;}


.wrapper{width:70px;top:1px;left:1px;}


.container {background:rgb(226,226,226);text-align:center;}

.bcontainer{background:black;width:71px;height:41px;}
.abc {
    
    
    border-right: 10px solid transparent;
    
}

.ab{    width: 61px;
    border-bottom: 11px solid black;
    border-right: 10px solid transparent;}