Step 1: What You'll Need:
Fresh, flat corrugated cardboard. Like, almost any cardboard box, bigger is better.
A sharp pocket knife or utility knife
A work surface you can cut on
A yardstick or some other straighedge and inch or two wide
some glue, like Elmer's (TM) or Titebond (TM).
Oh.....and at least one cat with claws.
Step 2: Getting Started:
When you have cut enough so that they are 5-8" wide when all stacked together you can start glueing. I use just a little trail of glue on each one. There is no need to completely cover the surface. Just a pencil lead sized line on each one is OK.
Spread the glue and squish the first two together. Then add the third, and so on, till you have the whole group glued and assembled. I use some clamps i have handy, but you could lay the whole thing on the floor, up against the wall and slide some heavy books up against it till the glue dries.
It makes a nicer job if you save out one strip, cut in half and glued against the end of the newly assembled scratching board. That will help to keep it all together when your cat really gets going on it.
It is nice to make all the pieces perfect.......or PURR-FECT, but the cats don't really seem to care if one or two strips might be a little bit off.
We use just a sprinkle of powdered catnip on the board to get the cats started and then they will have the time of their lives digging away. Flip it over when it gets worn. Recycle it and make another. Make lots and give them as gifts or sell them at craft fairs. Be nice to your cats, they might be the best friends you have.