JSFiddle - React, Tailwind, and code Playground

HTML

<div class="d1">
    <div class="sq">100500</div>
    k
</div>
<div class="d1">dfghfgh
    <div class="sq">100500</div>
</div>

CSS

.sq {
    width: 100px;
    background: yellow;
    position: relative;
    /*z-index: 0;*/
}
.sq:after {
    content:"";
    position: absolute;
    width: 90%;
    height: 10px;
    bottom: 4px;
    left: 8px;
    z-index: -1;
    transform: rotate(4deg);
    box-shadow: 0 5px 5px 0 gray;
}
.d1 {
    background: green;
    /*z-index: -2;*/
opacity: .99;   
}