I have no idea how to build this but my friend has one he made. It is a small drill that has a drill bit on it. It is places horzontally in metal sheeting with a small slit where the drill bit fits in and has room to spin. He takes the buds and runs them over this. i removes all fan leaves but does not trim to perfection. Also he loses alot of trichs so his hash from trim isnt that great. In my opinion unless you are trimming 5 pounds plus just get electric bonsai cutters. They work great and you are able to trim very close to the bud.