Welcome to tag along!
Fill one of the bowls with sand. Pile the sand up in the middle so that you get a “mountain” shape. If you want more of a bowl-shaped birdbath you have to make the pile of sand rather high.
Put the leaf on top of the sand and form the shape you want. Pile the sand up higher if you are not satisfied with the shape. You can use any leaf you want. I used rhubarb. Put some olive oil on top of the leaf and it will be easier to remove when the cement is dry.
Put cement mix in the other bowl, add water and stir thoroughly. The cement should have a crumbly consistency.
Cover the leaf in cement. Tap it with your hands ( use gloves ) in order to remove air bubbles. Cover the bowl in a plastic bag and let it dry. It takes approximately 48 hours to dry but it vary from cement mix to cement mix. Spray the cement lightly with water once or twice during the drying process.