Merging two hives with different size boxes

Hi All,
I had some of my bees swarm a few weeks back. I collected them back into a styrene foam box, the size that fits about 5 frames. I have progressively moved it back to the original hive. Now I wish to merge them. Have watched a few vids about the newspaper method. A couple of things. I believe I put the swarm hive on top of the super with the sheet of newspaper between? Is that correct? But the trouble is that the styrene box is much narrower than the flow hive so the lower flow hive box will not be completely covered.
What should I do.
Novice a treating swarms and merges.

Hi Steve. I’ve just posted a picture on a different thread. Transfer of nuc to hive
I used a board big enough to cover the space needed and cut a hole to accommodate both openings. So you could use a board to fit the Lang hive, put a nice big rectangle in it and cut most of the bottom of the polystyrene box off.

Having said that, you don’t want to merge a swarm with your existing hive if they both have queens.

Thanks for the advice.