Hi, Ryan,
I see. You want to delete the well that the clip goes in, not the clip itself.
I believe that the trailer templates are made to be used as is, and you can't remove the wells.
However, you can share your Trailer to your desktop as a Trailer (not convert it to a movie), then drag it into a newly created iMovie project, and there remove the wells that you don't want. Your Trailer will come into iMovie as one big clip. Extend your time line by sliding the slider lever near the Settings button that is located above the time line and to the right of your screen. Then you can split and delete out the displayed wells that you don't want. Another way is to place your cursor on the edge of the well displayed in the time line and, while holding down the "r" key and pressing your mouse or track pad, drag your cursor to outline in a yellow box the part that you want to delete. Then press delete on your keyboard.
-- Rich