Step 1: Get the parts
1. Glue: I used Titebond #3 Ultimate wood glue
2. Clamps: it can be done with 2 clamps, I used 24" Jorgesen clamps (#3724). Irwin clamps are also pretty good.
3. Wood! The most important part by far. Since this is a board that is going to have knives hitting it fairly regularly, using a hard wood is important. I used seven 2x2x20" red oak boards from Home Depot, who cut the boards to length for you. I think Loews has comparable wood. If you want a more expensive wood, walnut would work as well. Hard maple also looks very nice, and is considerably cheaper. I choose oak because that's what the local store had that day. The boards I got cost $40 altogether.
Note: Do not use tropical wood, as some people have allergic reactions to them. I personally have never seen this happen, but I have heard of it from two different people.
4. A decent power sander. This is helpful for smoothing the sides, top and bottom of the board after gluing. You can do this by hand using a sanding block, but it will take some time/effort.
5. A hand plane. You're going to need this to level the ends of the board, as the rough cut pieces of timber are not going to be exactly to length.
In addition to the above, a level work bench with good lighting and a wet cloth for wiping away excess glue are very helpful to have.