It kind of depends on the complexity of your dash. If you can make it out of one flat piece, make a template of thin cardboard or heavy paper. You can tape small sections together. Put the carpet upside down on a flat surface, put the template on it bottom side up as well and cut with a razor knife. I've done this for a flat dash and it was no big deal. If you have a raised section you can do it separately and then whip stitch the joints from the back side and follow up with carpet tape.