Soldering the circuit board.

Load a blink program onto the donor arduino pro mini clone, to make sure it works before you start doing anything else to it. After confirming it works load the neopixel strand test code on pin 7.

Next use a hot plate to solder the Atmega328p as well as to desolder the ADXL345 from its brake out board.

Next use a solder stencil to apply solder paste to the circuit board. I used a laser cutter to cut a stencil out of some adhesive vinyl, or you can order one from your board house.

Get the watch case 3d printed or milled if you are able to. I recommend getting it 3d printed in metal from shape ways in a material that is polished as it will save a lot of work down the road, you might be able to also find a cheap watch that has the needed inner dimensions, if so you would need to drill a hole and file it into a slot to be able to put the charging and programming connector.

Soldering the connector on the back using the 2mm concave headers is the hardest part as the headers need to line up with back of the case height, for this it is best to bend the header pins at a right angle and solder the tips to the pads on the back of the board. Then test fit it into the case making sure it lines up in height.

Adding the RTC back up battery and main lipo battery onto the back of the board.

Hot glue the battery to the back of the circuit board, making sure there is room for the headers on the side, test fit the watch module into the case keeping in mind that the headers need to line up with the slot on the back of the case.

Add the watch lens onto the front of the case making sure to apply even amount of glue to the inner lip that the lens sits on, apply it with a tooth pick and put very little because it could get on the view-able part of the lens.

Using paint to fill in the concave headers on the back of the case, let it dry then using 2 part epoxy to fill in the space between the headers and the watch case to make it water proof.