Phantoms for ultrasonography have been widely used to evaluate new medical devices and improve skills of new physicians. Several kinds of phantoms for ultrasonography have already been developed to keep pace with the progress of developments in ultrasonography. However, few reports exist regarding the establishment of physical measurement conditions such as size and density of scatterers. The purpose of this study was to develop a method for the construction of a phantom with scatterers in a single flat layer for use in ultrasonography. Firstly, a policy for the phantom with scatterers was developed. The scatterers should be a thin and flat layer in a transparent body. We selected a poly (vinyl alcohol) hydrogel (PVA-H) phantom as the body and glass beads as the scatterer material, based on this policy. A parabolic region at the top of the phantom may decrease the detectability of scatterers. For this reason, a surfactant was included in the PVA-H phantom. Phantoms including surfactants had better detectability of scatterers and fewer parabolic regions when compared with phantoms without surfactants. The phantom-based process was further improved by the use of an “upside down” method. In addition, the number of particles per area correlated with the weight of beads that were spread on the PVA-H surface using our fabrication method. In conclusion, a phantom constructed by the upside down process satisfies the developed policy.