JSFiddle - React, Tailwind, and code Playground

HTML

<div class="bookmarkRibbon"></div>
<div class="bookmarkRibbonRight"></div>

CSS

.bookmarkRibbon{
     width:0; 
     height:100px; 
     border-right:50px solid blue;
     border-left:50px solid blue;
     border-bottom:30px solid transparent;
}

.bookmarkRibbonRight{
     width:100px; 
     height:0px; 
     border-right:30px solid transparent;
     border-bottom:50px solid blue;
     border-top:50px solid blue;
}