A band saw would be even easier because you can lay the shaft on the table and get good uniform cuts rather than have most of the arrow waving around in the wind. I just don't have a band saw.

Because the blade on the band saw is so much thinner than the one I'm using you can make more than one cut to widen the slot as necesseary, just be sure to measure twice and cut once; that wood is horrible hard to put back on once it's cut out.

If you need links for buying the horn let me know. I got mine from a knife supply outfit. It comes in perfect slabs that were a breeze to cut up into what I needed. The buffalo horn looks way too cool when it's all polished up and the finish is on. One knife's worth will do a lot of arrows. They also have micarta and it may be even cheaper.