Ikea's stock of particles outside factory:
Maybe you have something nice that says it is made of hardwood. That means it has a thin layer of nice hardwood over top your crap fake wood. What I'm saying here is that I wanted to use some decent wood to make my table.
ninja stars, just sand it down, maybe reseal it. Try that on your BORGSJÖ.
lumber yard is the way to go. (No shame in harboring Home Depot love for you oak and pine fans.) The lumber yard has some precut planed stuff, but this stuff was unplaned, 14 feet long. For a small fee, they'll plane and cut it for you. That way it has a consistent width and 90 degree angles all over the place. We look the entire 14' 1-inch thick board and 18 inches from a 2-inch thick board (for the legs. We wanted 12 inches, but 18 was the minimum.). Plane time.
You can almost picture the table top here. Our next step is to glue and biscuit (like jamming a wood cookie into both edges) the 3 pieces together for the table top. Then we can treat it as 1 big table top piece and sand it down all together. Stay tuned.