According to some aspects, an additive fabrication apparatus is provided configured to form layers of material on a build platform, each layer of material being formed so as to contact a supporting liquid or a film disposed within a container, in addition to the build platform, a liquid photopolymer, and/or a previously formed layer of a material. The additive fabrication apparatus may comprise a container and a leveling element, wherein the leveling element is configured to move across a liquid-liquid interface to promote or create a flat interface between the two liquids. According to some aspects, the additive fabrication comprises a film disposed between two liquids, wherein the film maintains or provides a flat surface at the interface of the two liquids.