I recently built a new base for my J38 key which uses a piece of ceramic tile that I found at the local recycled building supply store for $0.25. The tile measures 6"x3"x0.5" and has nice smooth edges and sides all around the top. I heated the tile up on the stove and used hot glue to attach the key to the tile. Three of the four screws are just for show, they are also hot-glued to the key. The fourth hole holds the strain-relief for the wire. Drilling four holes into the tile would be a better solution than glue, but I think a diamond-tipped drill would be required for that and it would be difficult to do the job correctly. Hot glue can easily be removed by heating should I decide to move the key to another base. For the bottom of the tile, I cut a piece of 40 mil PVC rubber shower pan liner material and attached it to the tile with silicone caulk. I really like the feel of the key on the new base, it is small but heavy enough that it doesn't move around and the height is perfect for me. The smooth edges are easy on the fingers.