Student or Learner
Flat: flat position - in a position in which the surface of something is against another surface without curving or sloping:
- The bed can be folded flat for storage.
- He lay flat on the floor.
I would like to ask whether we can use 'flatly' instead of 'flat' in that meaning? The dictionary does not mention it so I feel confused about it.
- The bed can be folded flatly for storage.
- He lay flatly on the floor.
In this case, Longman has got it right.
In both sentences, only flat is correct. Whether you view it as an adjective or adverb makes no difference to anybody.