Graphene layers, hexagonal boron nitride layers, as well as other materials made of primarily sp2 bonded atoms and associated methods are disclosed. In one aspect, for example, a method of forming a graphene layer is provided. Such a method may include mixing a carbon source with a horizontally oriented molten solvent, precipitating the carbon source from the molten solvent to form a graphite layer across the molten solvent, and separating the graphite layer into a plurality of graphene layers.