I had the same problem. I used a largish prybar. Major PITA. Next time I'm making by dealer do it for me. Very poor design.
I think this design is for production ease. A guy with a little practice can snap those slides in in seconds, then it's done. No screws to position and tighten.
Everything seems to be going this way.
Remember back in the day, computer cases? The top and sides were one piece, usually hooked under the front, but held in the back with 4 or 6 screws. Now they just snap together, no screws needed. Car interior trim is another culprit. All that plastic stuff just snaps together, takes 2 seconds on the production line, but is hell to mechanics who need to remove it.