You are still missing the point. It still sounds like you are trying to output an odd shaped frame.
FIgure out what you want your final custom frame size to be. ..say 1920 x 500 make a project in resolve that is that size.
(if you are just trying to get your odd shaped footage to fill a regular screen, then thats a different process)
Import your media, and don’t allow resolve to adjust the project settings when it brings in the clips.
make your timeline, and resize your shots using the inspector to fill the frame you are now presented with.
Go to delivery page and output a file of 1920 x 500 (or what ever you are looking for) and you should have no black bars.
But it all starts by knowing what you want this frame size to be in the first place.
Glenn