Hey guys. Assume I’m completely ignorant. I’ve been researching for days to find a true UV (365nm) LED light to put on a project I’ve been working on. Anything preassembled is barely in the UV spectrum (395nm) so I’m wanting to build my own. I’ve found a 3W LED to use and a star PCB to put it on. It looks like I can use a soldering paste and hot plate to do this but when contacting the seller they said to use a thermal paste too. Is this needed or is that for attaching a heatsink to it once I’m done attaching the LED bead to the PCB? Attached is a pic of what I’m working with for step 1 of this adventure 
Welcome.
If the bottom of the LED can be soldered in the center, that would be best. Otherwise, I would definitely follow the mfg. recommendation and put some solder paste under there. And yea, a hot plate should work. I’d warn to remove it from the heat as soon as the deed is done, or further heat could do some harm.