<table class="GeneratedTable">
<thead>
<tr>
  <th>h1</th>
  <th>h2</th>
  <th>h3</th>
</tr>
</thead>
<tbody>
<tr>
  <td>1</td>
  <td>2</td>
  <td>3</td>
</tr>
<tr>
  <td>4</td>
  <td>5</td>
  <td>6</td>
</tr>
<tr>
  <td>7</td>
  <td>8</td>
  <td>9</td>
</tr>
</tbody>
</table>

.GeneratedTable {
  display: flex;
  flex-direction: column;
}

.GeneratedTable tbody,
.GeneratedTable thead,
.GeneratedTable tr {
  display: contents;
}

.GeneratedTable td,
.GeneratedTable th {
  display: block;
}

.GeneratedTable td:nth-of-type(1),
.GeneratedTable th:nth-of-type(1) {
  order: 1;
}

.GeneratedTable td:nth-of-type(2),
.GeneratedTable th:nth-of-type(2) {
  order: 2;
}

.GeneratedTable td:nth-of-type(3),
.GeneratedTable th:nth-of-type(3) {
  order: 3;
}