Edge Flange Interfering

I'm trying to add an edge flange but it interferes with the other flanges. I tried doing a cut on the corners but there's no option to just cut the one feature since all bodies are merged. I tried drawing a cross section sketch and extruding both direction to offset from the other surfaces but with this I can't get a proper flat pattern. And I don't know of any way to make the edge flange automatically trim corners. Also, I can't just do the edge flanges together because of the 4 degree slope on the top end (or at least I can't figure out how to). Any ideas? Thanks.

SolidworksParts And Features