SOURCE

<div class="box"> 
    <header>header</header>
    <main>
        <article>article</article>
        <nav>nav</nav>
        <aside>aside</aside>
    </main>
    <footer>footer</footer>
</div>

* {
            margin: 0;
        }

        .box {
            /* width: 500px;
            height: 500px; */
            background-color: #000;
        }
        header {
            position: relative;
            /* margin-top: 5px; */
            height: 100px;
            width: 100%;
            border-radius: 20px;
            background-color: #ccc;
            text-align: center;
        }

        main {
            width: 100%;
        }

        nav {
            position: absolute;
            width: 100px;
            height: calc(100% - 200px);
            border-radius: 20px;
            left: 0;
            background-color: #f00;
            text-align: center;
        }

        aside {
            position: absolute;
            width: 100px;
            height: calc(100% - 200px);
            border-radius: 20px;
            right: 0;

            background-color: #0000ff;
            text-align: center;
        }

        article {
            position: absolute;
            left: 100px;
            height: calc(100% - 200px);
            width: calc(100% - 200px);
            border-radius: 20px;
            background-color: #FFFF00;
            text-align: center;
        }
        footer {
            position: absolute;
            bottom: 0;
            height: 100px;
            width: 100%;
            border-radius: 20px;
            background-color: #ccc;
            text-align: center;
        }