Full Page Cover without Borders

Add an Image at master page whose size is equal to your page Size , You can further add text  &  Variables on top of it 

You can see page size from Format--> Page Layout--> Page Size and Image size from Right Click --> Object Porperties.

Thanks
Pulkit

In my own work, I put it on the background on a dedicated Master Page, often named Cover.Front. Page mapped by AMP (Apply Master Pages, based on some text tag unique to the front cover).

This presumes that the digital instance of the cover suffices (PDF, eBook) and/or the graphic objects don't extend to the page edge, or are exactlt the height and/or width of the page. Full-bleed at the print shop raises additional considerations, not the least of which is that they often want the back-spine-front cover as a single object, with the total dimensions oversize, including some content bleed.