Hi There,
It is the recent post element, you need to have post of course than on Cornerstone you can add the Recent Post Element and play with its parameters.
Regarding he slider, you can use a background picture in the first section (Put the posts on the second) and than you can add your elements to the the first section, like a Custom Title, Text, Button depends on what you want…
Than you can use the gap element using % to set the size of the section. When you add the gap it will occupy some space and you will be able to adjust how big you want it to be.
Hope that helps,
Joao