Stuff you need aside from the kit is a PJRC Teensy 3.2 (or LC if you just want the USB MIDI strumming function and no built in sounds), small but sharp sidecutters, a soldering station and some solder for electronics. Also recommended is a plastic tool (aka nylon probe or black stick) for safe and easy prying.

Place the capacitor. Watch the polarity. Positive side towards the Teensy, negative side (with stripe) towards the strumming area. Fold the capacitor over towards the chord switches to keep the profile low. Solder it in place. Cut excess off legs.

Place the tact switches. To make the back of the board as smooth as possible after soldering, fold the legs inwards over the solder pads. Use your plastic tool, if you’ve got it, to get them as flat as possible against the pcb. An alternative to folding them over is to cut them all after soldering. This method makes the switches align better as the flex in the legs is still there to keep it in position.

Place and solder the set of two angled pins for connecting to Teensy 3.2 DAC/14 and 24 pins. The angled pins are placed under the Teensy, inside the socket frame, pointing towards the strum pad. Make sure they sit level and with the plastic all the way down against the pcb. Solder one pin first for easy adjustment, and then the other one when it sits nicely. Cut excess of the header pin legs off at the backside of the board. Use protective glasses or at least close your eyes while snipping those legs off. The tend to fly all over the place, and I won’t take any responsibility for other people’s mindlessness :)

Place the 28-pin socket with the notch matching the print on the pcb. Fold the legs outwards to keep profile low and socket in place.

Place the audio jack.

Solder tact switches, socket and audio jack in place.

Cut excess off audio jack legs. Mind your eyes.

Mount the Teensy snugly against the socket:

• Hold the unsoldered pin header rows vertically against your work bench surface and push the plastic all the way against the end of the pins using a somewhat pointy and solid tool, like your sidecutters.
• Place pin headers in the side row holes of the Teensy, so the plastic is topside and legs hanging out on the backside.
• Place Teensy with the loose pin headers against the socket and hold it in place while turning the pcb over, placing it against your workbench surface. Press down on the back of the pcb, where the teensy sits, until the header pins pop in place into the socket. Be careful not to push or slip sideways or otherwise risk messing up the Teensy pin holes.
• Turn the pcb over again. With the pins set in the socket and the Teensy snugly agains it, solder the pins to the Teensy topside.
• Cut the excess off the pins (the plastic will keep the pins from flying all over when you cut the legs).
• Inspect the solderings on the Teensy before trying to remove it from the socket, and resolder any bad ones.
• If you are using the Teensy 3.2, use a plastic tool to pry up and remove the Teensy from the socket. Solder the short Dupont connection wires to the bottom of the Teensy. The longer one to the DAC/14 pin hole in the back row and the shorter one to the pin 24 pad. See video.
• Slide the Dupont connectors onto their corresponding pins inside the socket (Teensy 3.2 only). Use a plastic tool if hard to reach. Route the cables nicely under the Teensy and push the Teensy in place in the socket.

Use the Teensy loader app from PJRC to upload the hex file to the Teensy. Mind that there are different versions of the Chordstrum hex files for use with Teensy LC (got "tlc" in the file name) and Teensy 3.2 (got "t32" in file name). Test the completed Chordstrum by using it as per the usage instruction guide, while having it placed on a non conductive surface. Make sure you try out all the switches and touch sensors. If you are building the 3.2 version but not getting audio output, check the solder points and connectors of the Dupont wires under the Teensy.