If you're thinking of making trapezoid frames, then here's one method of converting a conventional frame:
Simply remove some wood from the Top Bar (detail):
And this is what results:
The joints are glued, using a partition board to ensure shape and side beespace are correct.
The lower bar can be glued, or made detachable (using panel pins) as shown, to allow further comb growth.
The modified frame installed in a K-TBH:
But would I recommend doing this ? No - I'm only posting this as another possible option.
Imho, if you want to run frames in a TBH, then making square-sided - Long Hive or Tanzanian-TBH - dimensioned to fit whatever frames you intend to use is a much better option - then frames can be swapped between box hives and Long Hives. And an extra advantage of frames over Top Bars is the ease of overhead feeding during winter.