SOURCE

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

  body {
            display: flex;
            justify-content: center;
            align-items: center;
        }
        
        .box {
            display: flex;
            width: 200px;
            height: 200px;
            border: 2px solid #ccc;
            border-radius: 10px;
            padding: 20px;
            justify-content: space-between;
        }
        
        .item {
            display: block;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            background-color: #666;
        }

        .item:nth-child(2){
            align-self: center;
        }

        .item:nth-child(3){
            align-self: flex-end;
        }