To add a Banner Slideshow under Header Squarespace, you can follow these
#1. Edit Page > Click Add Section
#2. Click People > Click section with (i) icon
#3. Hover on the section > Click Edit Content
#4. Click Design > Choose Banner Slideshow
#5. Result
#6. To make Slideshow behind the Header (Header Transparent), you can find the Page ID.
then use CSS code like this to Custom CSS box
#collection-66b3864c58666238eda7efb9 {
#page article section:first-child {
padding-top: 0px !important;
}
header#header {
background-color: transparent !important;
}
.header-background-solid {
opacity: 0 !important;
}}
Result: