The thumb piano, known as a kalimba or mbira and by many other names, is a lamellaphone that uses plucked prongs called tongues, keys or tines to generate acoustic vibrations. The length of the tine determines the pitch.
Generally, the thumb piano uses some kind of mechanism to create a great deal of pressure to anchor the tines across 2 bridges which allows the free lengths of the tines room to vibrate. The tines are usually of the same material and gauge (thickness) to ensure consistency so the pressure is distributed equally holding everything in place and in tune.
The method shown here is simplified and wonderfully versatile. It allows the use of more fragile, delicate, and unusual materials for the body of the instrument, and it provides a way to use oddly shaped tines of different materials at the same time while permitting the tines to be swapped out and tuned with ease.
There are interesting possibilities here: a simple armature or jig that becomes a tool with which to investigate the sound that different materials make - how they vibrate, how they resonate and how different combinations of factors can change the sound quality.
Experiment and explore and find configurations that work for you.
Video link in Step 6.
Step 1: The Grounding Bar
The bar shown is about 4 1/2 inches long and 1/2 inch in width.
The 3 empty slots are drilled all the way through, this is where fasteners can be used to attach the bar to something.