When growing things different people will get the same result different ways so whatever works for you is ok and my methods may not be best for all places.
Heel cuttings were the standard, esp for conifers but the industry has found that even better results come from a smaller, clean cut. The heel is usually torn from the main stem and is a bit ragged. It is also a larger wound than a clean cut so possibility of infection is higher. This is not a technique that is encouraged in commercial propagation now. It would be interesting to see what results you get making clean cuts on the stem Phoenix.
My simple set up is a shallow (about 2-3 inches deep) plastic tray with a couple of drainage holes cut in it,
I used shallow squat pots for cuttings for a while thinking drainage would be better but full depth 7 cm plastic pots seem to give me better results but as above, if it works, use it.
As mentioned above, junipers can take quite a while to strike. I just potted up some more from a batch taken almost 12 months ago. A few were still green and healthy but still no roots so I threw them away. Juniper cuttings taken now will strike quicker than the same cuttings taken in autumn, probably because it is warmer and the plants are actively growing now.