The stripboard is used for the 5 pots; jacks & LEDs panel-mounted and hand-wired.
Arduino Nano just about fits on the stripboard.
Nano accepts 12v VIN and provides 5v for pots (that means the circuit can be tested when powered by USB - don't connect Eurorack power at the same time though).
6HP panel size
Controls
Pot 1: clock speed coarse
Pot 2: clock speed fine
Pot 3, 4, 5: dividers/multipliers - CCW for divide, noon to duplicate master, CW for multiply.
Pushbutton: start/stop
Jack 1: master clock
Jack 2, 3, 4: divided/multiplied clock
LED 1, 2, 3, 4: visual clock indicator (2, 3 & 4 possibly bi-colour: green for mult, red for divide)
Issues and questions
Can the LEDs be "serialised" with the clock pulse?