Yes, at only 2ft deep they would work. For deeper wider ponds you would need to place them large face down. With cinder blocks it’s also worth building it slightly larger to add insulation material too. Adding the viewing pane may require angular steel or similar.
I built my above ground indoor pond 11.5x7.5x4ft (10.5x6.5x3ft finished dimensions) out of wood but cinder or breeze blocks would have been another choice but would have finished slightly smaller in internal size.