Final answer:
During the formation of foliation, flat minerals are arranged in a parallel alignment with each other.
Step-by-step explanation:
In the formation of foliation, the flat minerals are arranged in a parallel alignment with each other. This alignment can be displayed as parallel planes along which the rock splits or by overlapping sheets of platy minerals such as micas. For example, in a foliated metamorphic rock like slate, the mineral crystals are aligned parallel to each other, creating a planar structure.