Re-orient your iMac so it sits upright on the stand.

Insert a plastic card up into the corner of the air vent slot at the top of the rear case.

Push the card toward the top of the iMac to release the front bezel latch.

Pull the front bezel away from the rear case.

Repeat this process for the other side of the front bezel.

It may be necessary to apply several layers of duct tape to the top of the access card to aid in releasing the latches.

If the bezel refuses to release, try pressing the lower edge back onto the rear case and repeat this opening process.