The LEDs pictured require at least 8 volts to light in series, but they're being driven by less than 3, through a boost converter. The converter is a TI TPS61161, and was surprisingly easy to solder despite its small size and the thermal pad underneath, even with no solder mask and no solder paste. Surface tension really helps here. I just tinned the board using an iron and reflowed using a hot air gun.

I made the board using Pulsar's PCB Fab-in-a-box kit and direct-rub etch technique. Once I followed the correct set of directions it mostly worked, although I need to refine my technique quite a bit. They advertise 6 mil trace/space capability, but I didn't really get success until up to about 10.

The kit starts with a regular toner transfer pass, using a laminator instead of an iron. Then, you make a second pass with a green film that adheres to the toner, but clings much more tenaciously to the copper. The etching is performed by directly rubbing with a rough sponge rather than submerging. Direct agitation and abrasion causes the coper to be removed quite a bit faster than a regular etch tank.