Trying to take care of some basic crap on a relative's E46. All the little things you assume will be so easy...

Before I break something, someone please let me in on the magic spell I need to cast over the plastic rivets holding the left side interior trunk tray in place. See photo, these don't have the little slits implying "flat blade screwdriver" as found on the battery cover on the right side of the trunk. I've tried the obvious prying of the head but it's surprisingly difficult, to the point where I'm pretty sure something will break if I keep on prying.

I would like to remove this piece because there is some kind of gel-like substance such as melted candy or something pooled up in the bottom of the tray.