Untitled

<html>
<head>
    <style>
        .wrapper {
            display: flex;
            flex-direction: column;
            height: 100%;
        }

        .wrapper article {
            border: 1px #ccc solid;
            padding: 10px;
        }

        article {
            flex: 5;
        }

        .inner-wrapper {
            display: flex;
            flex-wrap: wrap;
            border: 1px #ccc solid;
            justify-content: center;
            flex-direction: row;
        }

        .video-box {
            display: flex;
            border: 1px #ccc solid;
            height: 130px;
            width: 190px;
            font-size: 60px;
            font-weight: bold;
            color: white;
            background-color: cornflowerblue;
            align-items: center;
            justify-content: center;
        }

        .add-box {
            display: flex;
            height: 260px;
            width: 380px;
            font-size: 60px;
            font-weight: bold;
            color: white;
            background-color: orangered;
            align-items: center;
            justify-content: center;
        }
    </style>
</head>
<body>
<div class="wrapper">
    <article>
        <h2>Videos</h2>
        <div class="inner-wrapper">
                <div class="add-box">Ads</div>
                <div class="video-box">1</div>
                <div class="video-box">2</div>
                <div class="video-box">3</div>
                <div class="video-box">4</div>
                <div class="video-box">5</div>
                <div class="video-box">6</div>
                <div class="video-box">7</div>
                <div class="video-box">8</div>
                <div class="video-box">9</div>
                <div class="video-box">10</div>
                <div class="video-box">11</div>
                <div class="video-box">12</div>
                <div class="video-box">13</div>
                <div class="video-box">14</div>
                <div class="video-box">15</div>
                <div class="video-box">16</div>
                <div class="video-box">17</div>
                <div class="video-box">18</div>
                <div class="video-box">19</div>
                <div class="video-box">20</div>
                <div class="video-box">21</div>
        </div>
    </article>
</div>
</body>
</html>