SMD LED went out quickly after I soldered it
What can I do differently now that I've ordered another damn $55 LED?


If you're certain current was ok, then the flickering makes me think you disconnected one of the bond wires on the actual AlGaN chip.  That would suggest you got too hot. 

Things you can do to improve your improvised reflow:


You can buy a thermocouple online for a fraction of what that LED costs.  Get one and check what the temperatures are without the diode in so that you get a sense of how fast the board is going to heat up.  Then tape the thermocouple close to the diode so you can monitor temperature while reflowing.  
If you aren't already, get 60/40 lead solder paste so that you minimize the temperature required.
If you find that the skillet heats up too much, one option is to not reflow with the skillet at all, but rather just use it to preheat to a safe temperature (e.g. 150C) and then use an iron to melt the paste.  This is more annoying but it gives you more control over the device temperature.   


If all else fails, you can also buy UVC LEDs presoldered onto starboards.