Glue the slats into a “stack”
Before gluing, stack your pieces side by side and take note of the grain patterns. Rearrange your slats to make the proper pattern that you want on the finished product. This pattern you make in your stack of slats will end up being replicated across the finished board. Randomly assembling the slats is easy, but if you just spend a few extra minutes to create a pattern, you can take the design up a notch and you will not regret it.
When you’re ready to glue, get your clamps ready first. I like to use a pipe clamp system so that I can rest the wood on the pipes, and really get good compression on the joints when gluing. Start from the left and liberally apply the wood glue onto the right side of the slat. I use Titebond III, as it is waterproof, and will really help your board live a long life – but other products may serve you just as well.
After the glue has been applied, I use a putty knife to spread the glue in a single layer across the whole piece, making sure to leave no wood area dry. Then move to the next slat, and repeat the process on the right side of each slat, all the way across. When all are wet, tighten your clamps just enough to get minor pressure on your pieces, but still allowing enough slack to move the pieces up and down.
Position your slats before clamping
Once in place, use a straight edge to flush up one side of the slats, and then clamp in place. Make sure you use as many clamps as you have access to. I like to have one on each end, and one in the middle. Sometimes, I’ll clamp on the top as well to keep the stack from bowing up under the pressure. You want a flush seal between each slat, and sometimes you can get minuscule spread between one or two slats if you don’t clamp in several spots.
Because you’ll be gluing these pieces again, you’ll want a smooth surface, so go ahead and use a damp cloth to wipe away the glue that has oozed through the cracks after clamping. Do this on both sides of the boards as much as possible. This will prevent you from having to spend extra time sanding or planing too deep before the next glue process. After cleaning the glue, let the glue for 24 hours.
Clean up the stack
After the glue has dried, you can remove the clamps, and your slats should be all stuck together and now sort of resembling a cutting board. Go ahead and run the ends through your table saw or jointer to create a flush end on each side. Now you’ve got 4 relatively flush sides on your piece. I now would run this through the planer again and take off only enough to give flat sides for gluing. Usually it is only 1/64th or less of an inch to take off of each side.
How to determine the width of the final end-grain cutting board.
Now, measure the new height of your stack of slats, and it’s time for more math to figure out how many cuts you’ll have to make to meet the width of the finished board you want. For example, if your glued stack of slats is 14 inches tall by 2 inches wide and you want a 16 inch wide cutting board, you’ll need to cut your stack of slats into 8 pieces. Those 8 pieces x 2 inches wide equals a 16 inch wide cutting board. Knowing that you need to cut the stack into 8 pieces, and the height of your stack is 14 inches… 14 inches divided by the 8 pieces you need equals a 1.75 inches for each cross cut. It also means that your cutting board will be roughly 1.75 inches tall.
Cross cut your slats on the cutting board into 8 equal sections. Keep in mind the 1/8th inch kerf from the saw blade when computing your widths. Again, a square fence on the table saw will make for even cuts and a level board.