Screen may not refresh to show empty battery if the battery is fully drained. It will refresh after a short period of charging when you attempt to power it on.
It is suggested in the overall guide comments that one could unclip all four side tabs and pry up from the middle of the left or right sides to get the two tabs from either the bottom or top out so that you can slide the cover off.
Use a wide flat-head screwdriver here and gradually work your way down to prying the battery free from the adhesive - battery is going to flex and bend. You're not going to want to use that battery again - recycle that old battery.
Slow down particularly near the bottom label where it is stiffer. Either that or I needed to give it more heat. Going too fast can risk tearing the rubber base if the adhesive is strong.
