JSFiddle - React, Tailwind, and code Playground

HTML

<div class="slide">
        <div class="arrow">
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer scelerisque ex eget ultricies blandit.</p>
        </div>
     </div>

CSS

.slide{
    position: relative;
    padding: 15px;    
}        
.arrow {
    max-width: 300px;
    background-color: #E01616;
    position: absolute;
    top: -10px;
    left: -10px;
    margin: 5px 0 0 5px;
    border: 3px solid black;
}
.arrow:after {
    left: 100%;
    bottom: 0px;
    content: "";
    height: 0;
    width: 0;
    position: absolute;
    pointer-events: none;
    border-width: 15px;
    border-bottom: 30px solid #E01616;
    border-right: 30px solid transparent;
}