<div class="grid">
  <header>
    Header
  </header>

  <aside class="sidebar-left">
    Left Sidebar
  </aside>

  <article>
    Article
  </article>

  <aside class="sidebar-right">
    Right Sidebar
  </aside>
  
  <footer>
    Footer
  </footer>
</div>

.grid {
  display: grid;
  grid-template-columns: 150px auto 150px;
  grid-template-rows: repeat(3, 100px);
  grid-gap: 1em;
}

header,
aside,
article,
footer {
  background: #eaeaea;
  padding: 1em;
}

header, footer {
  grid-column: 1 / 4;
}

/* Demo Specific Styles */
body {
  margin: 0 auto;
  max-width: 56em;
  padding: 1em 0;
}

.grid > * {
  display: flex;
  align-items: center;
  justify-content: center;
}