On mine, I added Pogos for 3V, GND, D28 and D29 (D28/29 can provide serial comms if needed, but the positioning also makes it easy to sit the Puck down nicely), then SWIO and SWCK - reset isn't really needed.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Would you be willing to share it when it's done? That's basically what I had planned as well - just 'shield' with pogo pins.
Personally, I'd copy the Puck.js board files from https://github.com/espruino/EspruinoBoard/tree/master/Puck.js/eagle into your design first, then you can use those to make sure you position the relevant pins.
On mine, I added Pogos for 3V, GND, D28 and D29 (D28/29 can provide serial comms if needed, but the positioning also makes it easy to sit the Puck down nicely), then SWIO and SWCK - reset isn't really needed.