The old method is to "slash" the bottom out with a long knife. Problem is the Sieraa dashes have raised corners, most of which have warped somewhat by now aswell, which makes the gap between the dash and the screen very tight. The screen corners dip down a fari bit behind the dash aswell. So it's very easy to do it when "knifing" them out - as said, even I have done it before now

But these days I use a thin guage square wire to remove the bottom of the screen (if it's a remove and refit, ie, saving the screen and not breaking it, I'd use the wire to remove the whole screen) and there is virtually no chance of cutting anything that way