I never thought this through until it's time to install the cabinets in a room that has (knotty pine) wood plank walls and ceiling. We'll have a filler piece between the wall and our tall cabinet. With a regular wall, I know how to trace the contour of the (uneven) wall and make filler piece to match it closely. But with these horizontal wood planks that have grooves, what's the best way to fit the filler piece? Both my hubby and I are total newbie to woodwork, but we did purchase table saw, miter saw, etc. and are willing to learn. So, what we are looking for is a solution that does not involve a lot of hand carving because we are short on time, but still provides an acceptable look and seal. Any suggestions?

Here is how our cabinet run will look like:

And this is how our wood planks look (although the ones we are working with are in a different room):