How can a customer 'Flatten a wooden placemat'?

[just4yougifts]

Hello,

As placemats can bend after pressing we have been putting heavy weights on them as soon as they have been pressed. However, a customer has contacted us and said that they are not completely flat. Is there any way that she can 'warm up the placemat and put some heavy weight on it'? i.e. oven, radiator, microwave? Obviously we don’t want to advise something that will affect the image on the placemat.

thanks
Lynsey