This used to be achieved with the code linked but since the dashboard code was heavily revised in Civi 5.33+? the old code doesn't work. Ref: https://forum.civicrm.org/index.php%3Ftopic=24355.0.html
My admittedly hacky solution is to add this CSS, which does work cosmetically but if a user doesn't already have a dashlet in your dashboard, they won't be able to add one.
.crm-container .crm-flex-box {display: inherit;}
How can I make this work better?
I don't particularly find the 2 columns useful to viewing many dashlets, but this would be a good feature improvement that could be a setting per site? Maybe per user?