Here is my file jig. I rough grind the bevel with a belt sanded and/or 4” angle grinder. Then finish it with this jig. I can adjust the bevel to any angle I want.
The thread rod is mounted solid on the work bench (in my case the shelving that is my temporary work bench). A piece of angle is the adjust pivot and has a hole thru it for the thread rod with nuts on top and bottom. The other leg of the angle has a hole for the file guide rod. The file guide rod is made from Beaman 500 arrow glued inside a 2020. The guide rod is glued into the hardwood file clamping block. The file is held by this piece. I clamp the knife and stop block with clamps.
With the cheap 1 X 30” belt sander I have, it take way to long and way to many belts to get a good bevel. With this jig I can get a nice flat bevel in no time. The only thing I would recommend different then this setup, is to use a half round file instead of a flat file. This is because it will be stiffer and you will get less deflection when appling pressure to the file.
Here is a full height flat grind I did last night.
Here is a fancier jig and where I got the idea from (along with my Lansky, same principal).
http://www.stoneandsteel.net/equip_antirock.html