Hello,
You can use the align attribute, but note that if you don't set a width for a table, it fits the whole page.
This sample is tested and working with MS Word and LibreOffice:
$html = '<table border="1" width="400" align="left">
            <tbody>
                <tr width="400">
                    <td style="background-color: yellow">1_1</td>
                    <td rowspan="3" colspan="2">1_2</td>
                </tr>
                <tr width="400">
                    <td>Some random text.</td>
                </tr>
                <tr width="400">
                    <td>
                        <ul>
                            <li>One</li>
                            <li>Two <b>and a half</b></li>
                        </ul>
                    </td>
                </tr>
                <tr width="400">
                    <td>3_2</td>
                    <td>3_3</td>
                    <td>3_3</td>
                </tr>
            </tbody>
        </table>';
$docx->embedHTML($html);
$html = '<table border="1" width="400" align="right">
            <tbody>
                <tr width="600">
                    <td style="background-color: yellow">1_1</td>
                    <td rowspan="3" colspan="2">1_2</td>
                </tr>
                <tr width="600">
                    <td>Some random text.</td>
                </tr>
                <tr width="600">
                    <td>
                        <ul>
                            <li>One</li>
                            <li>Two <b>and a half</b></li>
                        </ul>
                    </td>
                </tr>
                <tr width="600">
                    <td>3_2</td>
                    <td>3_3</td>
                    <td>3_3</td>
                </tr>
            </tbody>
        </table>';
$docx->embedHTML($html);
If you need to set the cell alignments, then you need to set td tags align, not the table tag.
Regards.