First I chose the connections I wanted to breakout and which should get adjustment knobs.
I pulled some potentiometer values from a hat and started making a schematic.
There isn't a nice header for ground, so I added a 1/4" connection just for the ground connection.
I also added a zener to protect the gate input. Note: the Werkstatt needs to be modified to safely accept a gate/trigger input. I simply severed the envelope generator's connection to the sustain switch.
Here's my schematic:
I like the roominess of 1590BB enclosures, so I used one for this project. I mocked up the parts in Inkscape and threw together this layout:
I printed it out as a template and drilled the case. Some paint, solder and dymo-tape later it looks like this: