Stepping stones become perfect birdbaths or cress pots with the help of a little card box lid. Place the lid where you want the indentation to be. Apply a layer of liquid natural latex around the edge of the lid against the mould so no concrete can sneak in between. If it is difficult to keep the lid from moving, secure it with double-sided tape. One tip for attractive edges is to brush liquid natural latex all the way around and even over the entire lid as a moisture barrier. When the natural latex dries, you can brush the mould and card lid with cooking oil. Mix the concrete according to the instructions on the package. Pour the concrete into the mould and shake to get rid of any air bubbles. Let dry for a few days.