This will ensure that you arrange the leaves in a thoughtful way rather than quickly rushing to push them on. Look at at the leaves you have and imagine how they'll look and try to line them up in readiness for pressing on the candle.  Hold it in place from the wick for 1 to 2 minutes. Ensure that it is all submerged. Place the leaves onto the softened candle surface, using tweezers. Press in place gently. Work quickly, once the wax solidifies, the leaves are stuck in place and no more can be added. The leaves will be sealed behind a new layer of melted wax. Further dipping in the hot water will shift the pressed leaves further into the candle. Bear this in mind if adding more layers of leaves, as some will be deeper in, some closer to the outside if you approach this in several goes. Aim for an even distribution. Let set. These candles will keep for a very long time, but you may need to infuse more essential oil after long-term storage.

Summary:
Consider designing the leaf pattern first. Fill the long jar with boiling water. Dip the candle into the water. Remove from the jar and place on parchment paper. Dip the candle into the hot water again. Drip a few drops of essential oil down the sides of the candle before it solidifies. Repeat with as many candles as you'd like to make.