First and foremost, ensure you have plenty of space, preferably outdoors. Alolan Marowak pride themselves on their dancing, and dancing is, on top of everything else, both a form of communication and self-expression for them. Unfortunately, the fire that lights up the bone clubs integral to such dances is very, very real, and as such, keeping an Alolan marowak can be a bit tricky … or, more to the point, costly for your insurance company.
That said, a sheltered place outside (such as a yard with a canopy over part of it) will be sufficient enough. Your marowak doesn’t need to stay out there, of course, and it would be best to ensure it has a bed inside to keep it out of the rain, but at the very least, it should be able to use this space for practice and enrichment. You can also kill two pidgey with one stone (as it were) by also constructing a place where it can train in this same area: simply clear a spot, line it with dirt, and add targets or practice dummies (a large stone or a log will be sufficient) to allow it to practice both its physical fire moves and its long-distance club-throwing moves.
Beyond training, it should be noted that although Alolan marowak are ghost-types, they are not nocturnal. On the contrary, they very much enjoy sunlight, and they’re happiest when sunbathing. You may wish to set up a heat lamp by its bed in order to give it a place to rest. They are also primarily carnivorous in nature, and besides the usual berries most pokémon will eat, they should be fed a diet of live insects, poultry (including eggs), or fish. Alternatively, kibble will do just as well. (Note: Standard marowak kibble is just as suitable for Alolan marowak as specialty/“Alolan blend” kibble, contrary to what kibble companies may have you believe.) Finally when it comes to the basics, be sure to give your Alolan marowak a dish of clean water; it’s a grave misconception that marowak in general don’t need a lot of water due to their typing, which is why many people believe marowak’s expected lifespan is far shorter than it actually is.
One last note: Alolan marowak are far more loyal than standard variations, as the rugged landscape of their native habitats have forced the entire Alolan cubone line to form strong friendships very early. Keep an eye out for any possessive or “clingy” marowak and be sure to train them firmly but gently to avoid separation anxiety or violence towards ex-significant others. Most Alolan marowak will get along just fine with their own teammates and trainers, but they won’t take kindly to anything that harms the people or pokémon they care about.
The Pokédex According to Bill 