Re-orient your iMac so it sits upright on the stand.
Insert a plastic card up into the corner of the air vent slot near 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. Or use two cards for the additional thickness.
If the bezel refuses to release, try lifting the lower edge of the front bezel slightly away from the rear case (detailed in the next few steps) and repeat the latch release process.
To lift the front bezel off the iMac, simultaneously:
Use your thumbs to press in the RAM arms and hold the iMac down.
Use your index fingers to pull the small bridge of material on the front bezel toward yourself.
Pull the front bezel up with your index fingers.
Once the small bridge of material has cleared the RAM arms, lift the front bezel by its lower edge just enough to clear the bottom edge of the rear case.
Lift the front bezel off the rear case and rotate it away from the bottom edge of the iMac, minding the camera and microphone cables still attached to its upper edge.
Peel back the EMI tape from the two vertical edges of the display.
During reassembly, it is helpful to use several small strips of tape to hold the EMI shielding along the left and right edges of the display footprint out of the way before lowering the display into the rear case of your iMac.
Disconnect both inverter cables from the inverter board.
These connectors are seated very tightly in their sockets. It is helpful to use your fingernails or the tip of a spudger to push the ears on either side of the connectors to dislodge them from their sockets. A small pair of hemostats helps a lot.