There is no screw on the side of the microwave
either. Any clue how to remove this?

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Did you go to the Frigidaire website and look for an installation
manual?

some instals have a safety latch, a small lever that you have to move to unlatch the oven. Sometimes this level is hidden or not obvious and the instructions are useful to located where and how to operate the lever.

when you move the lever, be prepared to support the full weight of the oven.

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