JSFiddle - React, Tailwind, and code Playground

HTML

<div class="square">
    <div class="circle">
        <span class="icon">i</span>
    </div>
</div>

CSS

.square {
    background-color: green;
    width: 200px;
    height: 100px;
    position: relative;
}

.circle {
    background-color: white;
    border-top-left-radius: 25px;
    width: 25px;
    height: 25px;
    position: absolute;
    bottom: 0px;
    right: 0px;
}

.icon {
    position: absolute;
    bottom: 0;
    right: 0;
}