Remarkably it's watered once a day - I leave it completely buried in a bigger pot, along with a number of others. Eventually they grow roots through the bottom of their own pots and into the big pot and generally make a party of it.
What's different? Well, there is no room for a design mistake because of the extremely limited number of branches. In the case of the Acer Campestre, individual leaves visually represent entire foliage pads.
Often, in this size, they only look good while the leaves are coming out - so defoliating one or more times a year is quite typical.