Website Under Construction Setup

I am looking for a skilled freelancer to help me set my website to 'under construction'. This means I need to hide all existing content and display a simple message indicating that the site is currently being updated. The ideal candidate will have experience with website management and can quickly implement this change without disrupting any ongoing processes. Your expertise will ensure that visitors are informed while we work on improving the site. Please provide examples of similar work you have done in the past.