This video uses the Elevate "block" feature to place the right corner -- these are square corner designs that work best using the Elevate only.
Essentially, we set the left corner first then flip (or rotate left) the design to place in the right corner...remember we want these designs to face the border/each other so the borders flow and connect between them.
Creative Studio has a border/corner feature that can be used to interview, size and create patterns for the Elevate with much more detail and control -- gives you a complete visual of the two corners and the border connected between.