JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
</div>

CSS

.wrap{
    width: 600px;
    outline: 1px solid #fff;
    overflow: hidden;
}
.wrap div{
    width: 200px;
    height: 200px;
    outline: 1px dashed #ccc;
    float: left;
    display: inline-block;
    position: relative;
}
.wrap div:nth-child(2):before,
.wrap div:nth-child(2):after{
    content: "";
    position: absolute;
    width: 30px;
    height: 30px;
    background-color: #fff;
    z-index: 1;
    left: -15px;
    bottom: -15px;
}
.wrap div:nth-child(2):after{
    left: auto;
    right: -15px;
}