JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
    background: #f06 ;
    background: radial-gradient(circle at 0 0, transparent 20px, #f06 0),
                radial-gradient(circle at 100% 0, transparent 20px, #f06 0),
                radial-gradient(circle at 100% 100%, transparent 20px, #f06 0),
                radial-gradient(circle at 0 100%, transparent 20px, #f06 0);
    background-position: top left, top right, bottom right, bottom left;
    background-size: 50% 50%;
    background-repeat: no-repeat;
    
    width: 300px;
    height: 200px;
}