A method includes placing at least one mold along outer edges of one or more first pieces of fabric. The method also includes forming free-standing flexible walls and a floor of a containment structure by depositing liquid-impervious material onto the at least one mold and the one or more first pieces of fabric. The floor is formed seamlessly with the walls. The method further includes forming flexible supports by depositing liquid-impervious material onto multiple second pieces of fabric connecting the floor and the flexible walls.