JSFiddle - React, Tailwind, and code Playground

HTML

<div class="ribbon">
    <div class="ribbon-body"></div>
    <div class="ribbon-right"></div>
    <div class="ribbon-left"></div>
</div>

CSS

.ribbon{
    float: left;
    margin-left: 10px;
}

.ribbon-body{
    background-color: blue;
    width: 40px;
    padding: 10px;
    color: white;
}

.ribbon-right {
    float:left;
    width: 0; 
    height: 0; 
    border-top: 30px solid red;
    border-bottom: 30px solid transparent;
    border-left: 30px solid blue;
}

.ribbon-left {
    float: left;
    width: 0; 
    height: 0; 
    border-bottom: 30px solid red; 
    border-right:30px solid blue; 
    border-top: 30px solid blue;
}