We installed IKEA cabinets that are 15" deep (15.5" with the doors) and we have a GE OTR microwave that is 16" deep. So we need to bump out the microwave in order to open it. We see GE sells a kit, which is $130 and it bumps it out 3". This seems excessive. Is there another solution to this issue?
The simplest and most cost effective solution is to use a wood frame. The frame can be painted or stained to match the cabinets or wall. Most of the OTR microwaves I have installed have a metal track at the bottom that screws to the wall first that the microwave hangs on and two screws at the top that connects it to the upper cabinet. If this is the case you could recess the frame to better conceal the lumber.