This is a stone holder I made yesterday from some scrap plywood. Dimensions are 30cm x 8cm x 5.5cm tall, *7.5cm tall (*at end with lift). The block slides in a slot and locks with carriage bolt and wingnut on bottom, hardware is stainless. Takashima Awasedo on base and Choseras without bases fit within the clamping space; could easily be made longer to accommodate larger stones. I wanted to try an angled base so I added an extra foot that attaches in two holes with pegs; which I really like. I will try to get an after-use photo (maybe with its first job), this thing is all green and black now from swarf.
I encourage anyone interested to use my design, or improve upon it, if they please; open-source for the KKF community.