the “Gallery Flip” is working with the attached images to this page, so you don’t need to setup the the allslider for this gallery. Just create a new page, choose “Gallery Flip” as slideshow and upload the images you want to have in the slider. WordPress will attach the images while uploading to this page. Then publish the page and all is done.
Please go to WordPress admin -> Appearance -> Theme Options -> General -> Extra CSS Content and add this:
This code will remove the overlay.