bowed cupboard doors

[reddaren]

i have just built some cupboards in my house using wickes furniture board. The top set of doors i have cut a hole in to allow viewing of the other halfs vast ornament collection .Trouble is doors have bowed considerably. each door measures about 500mm X 450mm with hole inside 400mm X 350mm. Any one tell me how to get the bow out
Many thanks in advance to any one who can help

 

[renovator]

the panels in cupboard doors should be floating i.e. unfixed, to allow for expansion/contraction.

commonly the easiest means of achieving this is to create a slot in the top and bottom rails and the stiles ( side rails)

Additionally, natural wood should be stored in the environment in which it is to be used for around 14 days to allow it to acclimatise to the local heat/moisture content.

what is the construction of your doors?