JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
    <div class="left"></div>
    <div class="right"></div>
</div>

CSS

.box {
    position: relative;
    width: 200px;
    height: 200px;
    padding: 5px;
    background:lightcoral;
}

.left {
    position: absolute; /* ------ Get Rid of these lines */
    bottom: 5px;        /* ------ */
    width: 80px;        /* ------ */
    overflow:hidden;
    height: 20px;
    background: lightyellow; /* Take up rest of space */
}

.right {
    float: right;
    width: 100px;
    height: 100%;
    background: lightblue;
}