gap above microwave in kitchen

[Galey2000]

Hi, thanks for all your suggestions so far guys

 

[foxhole]

If you don't mind it looking odd I suppose, in any case it's irrelevant to the OP, top or bottom he has a gap which needs to be filled with something.

No, the current microwave is sitting on shelf , built in units come with metal rails that sit underneath the micro wave and raise it to allow 360 ventilation around it which mean a spacer on the face is required to hide .