I couldn’t find a picture before we bought this for our mini-kitchen-cabinets in progress (more on this soon! It’s been hectic.) but here is what an IKEA Karlby walnut + particleboard countertop looks like on the inside:
This is the countertop (picture from IKEA website):
And here’s the difference before and after learning to cut it properly (compare both cut edges):
The trick, with a circular saw: cut it with the good side down, put blue tape over the cut line before cutting.
We are learning so much! I am currently stressing a little over a drawer handle that is the teeeensiest bit unlevel and hard to fix because we can’t easily patch holes in the white laminate. It’s probably okay.