Well we shall get two cells stuck together, and if the next division is in the same plane four and if the next division is in the same plane we shall have made a chocolate orange. The metazoan has established shared food supply, faster swimming and protection from its large size. So there is no pattern. If a pattern arises, that is if cells become different from each other we have to find a reason, a mechanism. Well how about this.
Lets suppose that the blastaea lives in a gravitational field, probably the sea.
No matter what its overall density we can bet that not all the cytoplasmic contents of the blastaea are equally dense, oils and fats will be lighter than proteins and carbohydrates. In an egg cell, a gamete, they will tend to layer out. So the egg could be the source of pattern and pass it on to the embryonic cells. Or the blastaea itself could acquire pattern from the environment in another way. Air is a discouraging medium for a marine animal, so lets suppose it sinks.