.layout {
  width: 100%;

  display: grid;
  grid:
    "header header header" auto
    "leftSide body rightSide" 1fr
    "footer footer footer" auto
    / auto 1fr auto;
  gap: 8px;
  grid-auto-flow: column;
}

.header { grid-area: header; }
.leftSide { grid-area: leftSide; }
.body { grid-area: body; }
.rightSide { grid-area: rightSide; }
.footer { grid-area: footer; }
<section class="layout">
  <div class="header">1</div>
  <div class="leftSide">2</div>
  <div class="body">3</div>
  <div class="rightSide">4</div>
  <div class="footer">5</div>
</section>