What is a "cover panel"? Is that a panel matching the doors that mounts on a cabinet side? You need a panel matching the cabinets at the end of the dishwasher to hold up the stone and add the cover panel to it.

Did you talk to the kitchen design help at Ikea about this?

Is this going at the end of a run with no adjacent wall? If there is a wall, you don't even need the panel (aside from looks), you could just attach a Fixa bracket to the side wall and back wall and the stone can rest on that.

Maybe a picture of your situation would help but Ikea is really the place to go .