Fantastically simple explanation of how to get it done. Thank You!

thanks for the instructions, do you have a video with the results? I'm trying to do something similar =)

Very clear instructions. I have a similar situation, but have a question. I am scribing a filler in between a wall and a cabinet. The space is 5" wide at the top and 4-13/16" at the bottom. So just 3/16" has to be removed at the bottom third of the filler where the wall starts to tilt in. The cabinet is already installed. I can't fit the 5" wide board in there obviously since it exceeds the width of the narrowest point. Do I take the cabinet out? Then, how do I cut such a small sliver that tapers to nothing? It's barely wider than my jigsaw blade and I have nothing to hold my saw in place at such a flat angle to make a precise cut. Any suggestions? Thank you in advance!