JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer">
<div class="cornered">It's possible to put text up here, too
    but if you want it to follow the slant you have to stack
    several of these.</div>
<div class="main">Hello hello hello hello
hello hello hello hello hello</div>
</div>

CSS

.outer {
    background-color: #ccffff;
    padding: 10px;
    font-size: x-small;
}
.cornered {
    width: 176px;
    height: 0px;
    border-bottom: 40px solid red;
    border-left: 40px solid transparent;
}
.main {
    width: 200px;
    height: 200px;
    background-color: red;
    padding: 0 8px;
}