Amazon’s fees to pack combo/bundle packs for FBA?

I currently run 5 products through FBM and have a 3PL who does the picking and picking. I can send my product to them in Cartons of 12 and they will assemble the order as necessary.

E.g. customers can order in single units, or can choose one of a handful of bundle packs.

I presume that Amazon can do this as well but what are the requirements? Given the difference in size between my 3PL and Amazon I’d imagine Amazon would be more strict in their requirements?

As it stands I don’t have to do anything special. Just ship product to my 3PL and then it’s their problem.

What headaches am I taking on if I were to move to FBA and need Amazon to do that for me as well?