I made a little tin foil pan with a handle and did mine on the stovetop electric burner . One of the easiest things I've ever done as far as modding. Simple as pie .(actually pie is much more difficult)
Don't forget
November is national mod month
I ended up using the electric stove too 
compared to soldering iron, simplest way so far, just gotta know your technique… But djozz butane torch method is definitely the fastest and gets the job done.
I always add some flux in this case, even better results.
For my recent reflow, i always apply a tiny bit of pressure on the dome to ensure there is no gap in between the emitter and mcpcb. Probably, i should try solder paste next time.
I use both the stove top and the butane torch methods. Sometimes at the same time when reflowing the pcb to a large copper pill. A foil wrap works well to keep the pcb centered on the pill and the solder won’t stick to the foil.
Yup, once the emitter floats, give it a tiny bump with the tweezers to make sure surface tension pulls it back…then a light bop on the dome…then from the bottom hit it with a rubbing alcohol soaked paper towel…ahhh…the sizzle
First reflow I’ve done is on a smallest gas cooking stove covered with copper sheet. I heated it too much and killed it ( poor litle xp-g2). Later I was using soldering iron with great success with aluminum mcpcbs but it’s not very suitable for noctigons and copper sinkpads because bits of solder always catches under mcpcb where soldering iron tip was in contact and must be removed after, wich is not very convenient. If someone else is using this method for reflowing emitters on copper I recommend using piece of aluminim foil between solderig iron and mcpcb. I’ve also done few single and multiple emitter reflows with gas torch and had great success. Note that I have used soldering paste so it’s much harder to overheat mcpcb and emitter because of it’s lower melting point and you can see better when it melts. Even though I’ve used soldering paste, I found need for pressing emmiter down when soldering paste is still hot and liquid in order to have best possible electrical contact and thermal path. Only problem that might appear is not well centerd emitter so you need to reflow it again if you are tight with space in the pill. Since one month or so, I’m using smd rework station for my reflows and it’s by far most convenient method I’ve used so far. Applying heat is more gradual than any of the previous methods I have tried and it’s a lot easier an cleaner.
I am doing the exact same way as how Justin does it: using a soldering iron underneath, that’s it.
I starred at the reflow temperature vs. time graph in CREE spec sheet for a while and told myself, “Man, this can’t be true…”.