Detached ads aren't part of a graphic. You add them to a playlist as their own item and choose exactly where, when and how long they show.
Add a detached ad
Open the playlist and click Add Item to Sequence > Add advertisement.
Choose the kind of ad: an image ad (a specific size from one of your ad sets), a custom image (any size you've uploaded as a custom image in an ad set), a video ad (a video uploaded to an ad set), or an ad slot for the home or away club to fill.
Choose the position on screen, e.g. top right.
Set the start time and duration. Leave the duration empty and the ad stays on for as long as the playlist is running.
Save the playlist.
Create an ad slot for a club
Choose Ad slot.
Name it after where it plays, e.g. "Pre-game opening ad".
Choose the size the club must supply. Custom lets the club choose.
Choose Home or Away.
Set the start time, duration and position.
Save.
The slot appears on the Ad slots page of the club's portal, grouped by playlist. The club adds their image, and it plays in their slot for the time you set.
Ideas
A sponsor on every goal, placed away from the goal lower third.
A rotating set of sponsors at half time.
A sponsor every 10 minutes using time triggers.
A sponsor with every third corner using a milestone.