Since this was an early prototype, we first designed the PCB to be one layer and with through hole components. There will be at least 2 more versions:
-Dual layer THT (for kits)
-SMD version (for the pre-assembled variant)
We designed the PCB according to the datasheets of each component (Note the L293D does not have thermal relief pads on the ground pins, so the ground plane can act as a heatsink ) and according to standard design rules.
As for design/CAD software we basically had 2 options: KiCad an EAGLE.
We finally decided on KiCad, even if it's a bit harder to work with mainly because this one is open source and does not have any restrictions, like EAGLE (max number of layers / Use is limited to non-profit applications
(This was the only acceptable screenshot I could find of the design process. Besides, we still have to rule out some quirks before we release/licence the design)