JSFiddle - React, Tailwind, and code Playground

HTML

<div class="left">
    <div class="left-main">
        Left
    </div>
</div>
<div class="right right-main">
    Right
    <div class="bottom-right">
        Bottom Right
    </div>
</div>

CSS

.left {
    float: left;
}
.right {
    float: right;
}
.left-main {
    width:200px;
    height: 400px;
    background-color: red;
}
.right-main {
    width: 100px;
    height: 30px;
    background-color: green;
}
.bottom-right {
    background-color: blue;
}