After doing some serious mods to the stock knife, I used some red oak that I bought from the hardware store. It was like $2.60 for a piece 2x.5x48, I think. You can see how after sanding to 1000 grit and treating with oil, the color really changed. Since these pics, it's gotten even darker, which looks cool!
For the scales themselves, I did some very rough shaping with a saw and sander before gluing them on. Once on, I had to thin them out so I (dangerously) used a miter saw. Then I trimmed a little more around the outside with a hack saw and then used files to get it down to the metal and to make the basic contours. From there I used 80, 120, 400, and 1000 grit sandpaper.
Of course, when you make them, keep in mind whether you want to still use the original sheath. Neither Alude's or mine will actually still work in the sheath (you could mod the sheath to work with Alude's though).
When making yours, you might want to consider following the KaBar micarta pattern, which is designed to still use the sheath and bottle opener.
Or do a search to find some more custom BK-11 scales for more inspiration!