Heat an iOpener or other warm compress, and let it sit along one short side for a minute.

Then, attach an anti-clamp or similar suction cup to the middle of one side, close to the edge. Don't press down too firmly to 'set' the suction cup -- the glass is thin!

Lock the Clamp, and slowly crank it open just 1 turn. If the adhesive isn't loose enough to let the glass lift in the middle, apply some more heat while doing this.

Once a small gap appears, insert your metal slicing tool about 4mm, release the Anti-Clamp, drip some alcohol in along the whole edge, and apply heat again.

After the heat and solvent have worked for ~30 seconds, remove the compress and start wiggling & sliding your tool up and down the edge. Try to free the whole edge, and slide just around each corner, then go to the opposite short edge and repeat.