Once you’ve decided to have a Coming Soon page, you can go with the “Coming Soon” Page which is installed with the dummy-data or you can build a page from scratch and use that one.
At the the bottom of editing page in the “Theme Oprtion” box you need turn off
- Top Header
- Ttile wrapper
- Bottom footer
This make blank template only with main content
To use this page as Homepage, navigate to Settings → Reading and choose your “Coming Soon” page.