I just assume as soon as one touches the other they fizzle out. I guess the top of the box gets cut a bit.

It’s like folding space. They basically occupy the same location. Its just two “sides” of a 2D plane. The portal can’t go into itself.

Worst case if it can it’s like bottle so they just flip positions and the whole thing reverses and the box just comes right out and the colors swap.

Nothing crazy.