Cut the base on CNC and assembled buttons and joysticks. Tested mouse operation with a breadboard.

Everything looks sturdy, the plastic parts are solid and have zero play. The wrist pads felt too thin for my hands, so 3-mm inserts were printed -- note the blue inserts between the base and the wrist pads.  The STL files have been modified for the extra thickness.  I have also made the files which combine the wrist pads and the switch slots for printing in one go.

The original plan was to print the joystick caps from a semi-transparent filament to make them glow in the dark (both joystick boards have LEDs).  Well, no filament for now, may replace later.