There is ongoing research in freestanding single-atom thick elemental metal patches, including those suspended in a two-dimensional (2D) material, due to their utility in providing new structural and energetic insight into novel metallic 2D systems. Graphene pores have shown promise as support systems for suspending such patches. This study explores the potential of Sn atoms to form freestanding stanene and/or Sn patches in graphene pores. Sn atoms were deposited on graphene, where they formed novel single-atom thick 2D planar clusters/patches (or membranes) ranging from 1 to 8 atoms within the graphene pores. Patches of three or more atoms adopted either a star-like or close-packed structural configuration. Density functional theory (DFT) calculations were conducted to look at the cluster configurations and energetics (without the graphene matrix) and were found to deviate from experimental observations for 2D patches larger than five atoms. This was attributed to interfacial interactions between the graphene pore edges and Sn atoms. The presented findings help advance the development of single-atom thick 2D elemental metal membranes.