JSFiddle - React, Tailwind, and code Playground

HTML

<table>
 <tr>
  <td colspan=2>top</td>
 </tr>
 <tr>
 <td class="left">left</td>
 <td>right</td></tr>
</table>

CSS

html, body
{
 height: 100%;
}

table
{
 border-collapse: collapse;
 width:  100%;
 height: 100%;

}

.left
{
 border-right: 1px #aaaaaa solid;
 border-top: 1px #aaaaaa solid;
}