On our K50 Elite, the lid is held on with 2 screws, and two tabs (which I broke off) near the rear. I think to remove the lid, you first take out the 2 screws, under the cover on the front, and then slide the lid backwards to clear the tabs. I attached the rear of the lid by 2 spots of hot glue where the tabs used to go. I also removed the handle before removing the lid.
I used dental floss - had to double it - and that worked the best. However, as I lifted the end nearest the phone top, the very bottom part was still stuck, and that part bent away from the battery body, still attached. A voltmeter showed no charge on the little terminals, so I went ahead and ordered new battery. I found the directions about pulling the tab of the adhesive (after splitting it) later and will try that next time.