首先看一下效果

HTML

<div class="wrapper">
        <div class="box">
            <div class="item"></div>
            <div class="item"></div>
        </div>
        <div class="box">
            <div class="item"></div>
            <div class="item"></div>
        </div>
    </div>

CSS

 		.wrapper {
            border: 1px solid salmon;
            background-color: salmon;
            width: 300px;
            height: 300px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
        }

        .wrapper .box {
            display: flex;
            flex-direction: column;
            justify-content: space-between;
        }

        .wrapper .item {
            width: 100px;
            height: 100px;
            background-color: aquamarine;
        }