In the sections below we list required and optional tools and assembly materials, including multiple options where appropriate. Assembly of all three circuit boards proceeds by first attaching all of the surface-mount chips (resistors, capacitors, microcontroller, etc.).  When assembling the boards individually, hand soldering works well either with a temperature-controlled soldering iron or hot air work station.  When assembling the boards in large batches, we used an Arduino controlled reflow oven from plans found on the internet (link provided below). Once the surface mount chips have been attached, the various through-hole components (headers) and additional surface mount components found on the backsides of some boards can be hand soldered on to complete each board. We used this step to also perform quality control on the soldering by using a magnifying glass to visually check for bridged contacts.

The video demonstration of the assembly steps below is also linked from the OWHL GitHub repository.
Click here for a high-quality version of the video.