I always place a clamp where I need to apply pressure to close up a gap, Saying goes that one can not have too many clamps.
Problem with box joints is sometimes the fingers will stick out a bit and not allow a caul to work. Usually, a box joint will need clamp pressure from two directions.
Try this: use the fingers of both hands, mesh them together like a box joint....Then move one finger where a clamp might be....do the other move with it?
One could set the clamp so pressure is applied up and down on the corner of the box....but then you'd need one on each corner...and then, how to pull the box into square.
This "Too many clamps" thing is just .....BS.
almost sounds like they never made such a box, before.
I Use the amount of clamps I think are needed, to pull ALL joints tight and square.....and, when one add a bottom to the box, and needs to add clamps the hold that in place, too....
A "forest of clamps" is however many clamps I feel are needed to get to tight and square...before the glue sets up. Not one more, and not one less.
YMMV...