Pretty basic idea: 6in Tapered Candle Mold.

Just print both halves, bottom up with organic supports - to hopefully produce as smooth a mold as possible. 

Should produce a tapered candle about 6 inches long with a ¾ inch base. 

I'll post updates after I've had a chance to use it. 
 

The idea is to use wood clamps or spring clamps (perhaps rubber bands or masking tape…) to keep it together and then just knot the wick on one end and pull it tight to the other, use a binder clip to keep it taut. poor liquid wax in top. and then push a small knife or screw driver into the slot to split the two. 
(I suggest using plumbers putty or sticky tack, perhaps a little bit of modeling clay. to cover the hole until the wax is solidified.)

+++

if  you utilize the “…-6inCandleMold_28deg_round” at 0.3mm you can print them both in just under 5 hours, jumps up to 7 hours at 0.2mm layer height.

with:
3 perimeters 
30% cubic infill
24mm brim
organic support [everywhere]

enjoy!