I have found that the larger leaf cuttings produce bigger new growth compared to smaller leaf cuttings. So, I would wait for healthy large leaf to do cuttings...of course, if you're impatient and want to do leaf cutting on a small leaf, you'll have a very small off-shoot
Leaf cuttings do not require the trap to be present, just the white portion (rhizome). Never let the soil go dry. It's best to cover the pot with plastic and expose to indirect sunlight to prevent "cooking" the little guy
Leaf cutting is very simple, but it does take time...so give it a good 4-8 weeks for new growth.
Because summer is half way over, any new growth from your leaf cutting will not need a dormacy this winter, just a LOT of good light during the winter