Step 1: Get your materials
Step 2: Getting a square deal
Step 3: It is not OK to eat varnish
Here you can see N. passing them through a planer to take off the outermost layers of varnish and wood so we could get back to clean maple. We passed through each face that glue would be applied to several times to get a nice smooth surface. We left the varnish on the faces that would become the cutting surfaces to be dealt with later.
Step 4: Check your work
As a related aside, you can see we were wearing ear protection, which is key.
Hearing is one of those things, like eyeballs and fingers, you want to hang onto for as long as possible.
Step 5: Make it go faster
Step 6: GLUE!
Even on your face.
Wear a helmet.
EDIT: We used regular Titebond for this project and it's held up fine for me over the past 5 years. In the meantime I've switched to Titebond III which is their waterproof glue. It's more expensive, but I think the added protection/precaution is worth it.
Step 7: Line 'em up!
This is a nice shot, because it illustrates some of the things I mentioned earlier. You can see that we left the varnish on two of the surfaces and that we also didn't worry about length at this point.
Don't be mislead by this last statement! For clarification, we'd decided (based on the number of pieces we had) how big and how many of each cutting board we wanted to make. I mean "not worrying about length" in terms of not being ultra-precise about the lengths of the individual pieces PER cutting board. You can see the cherry racing stripe is quite a bit longer (and thinner) than the other pieces.
Step 8: The Clamp Down
Step 9: Sit down and have a think. Or two.
All it takes is about 30-45 minutes! Different glues cure differently and wood glue cures in the absence of air, which is why you want to be so careful about making sure there aren't any air pockets in your glue job. The pressure from the clamps forces out all of the air in between the slats and so the glue cures very quickly. Just enough time for a pint. ...better make that two pints, just to be sure.
Step 10: Operation "Reverse Clamp Down"
Grab a paint scraper and a scrap of something to wipe the glue on (it will still look wet on the surface, don't worry, it's cured between the boards themselves), and get all the excess crud that got squeezed out during the clamp-down. You only want to leave as much glue on the boards as you'd want to send through your planer.
Step 11: The plane boss, the plane!
Step 12: Tying up loose ends
Step 13: Sanding
Step 14: The Finishing Touches
We added a chamfer (45 degree angle) to the boards giving them gently rounded outside edges and gave them another light sanding by hand to catch all the side-surfaces.
Step 15: Fin.
In terms of protecting your board, use mineral oil, or one of the commercially available products for protecting butcher-blocks. Vegetable oils will go rancid and you'll want to avoid nut oils so you don't send anyone to the hospital with an allergic reaction. Whatever you decide to use, remember that it needs to be food safe.
If your board starts to look dry, just reapply your mineral oil by rubbing it into the surfaces (every side, keep it evenly oiled) with a cloth. You really can't use too much and it probably wouldn't hurt to do it a couple times, i.e. apply oil, let it sit overnight and hit it again the next day.
You don't want to expose these to too much water - do not put them in the dish washer, or let them soak - if you scrub it off with soap and water be sure to dry it immediately. The more you wash it the more often you should apply oil to keep it in good shape.