Here's a mini-Altoids box (with a regular one for comparison):
Much too small to fit any jacks. There are 2 holes with grommets on the side for wiring, and these jacks will be external. The lithium battery fits inside.
The holes for the pots are not exactly lined up, 'cause I eyeballed the drilling. Oh well, I'll do it better next time.
It's finished except for the wiring. Two pots, a DPDT switch for true bypass, a charger board for the lithium battery (bottom left), a booster board to triple the battery voltage (top left), and the actual effect (right).
The lithium battery charger has a USB port that pokes through a hole on the left, so once it's wired, I won't need to open it again.
What is it? - a silicon Harmonic Percolator. I love this circuit. There are a couple extra (unfilled) pads for the diodes, but I prefer it without them anyway.