Step One (Prepare Workspace):
Assemble all materials and read all steps before proceeding. Colouring the concrete or painting/decorating it is optional. Work in above freezing temperatures, in a garage or outside in a shady area if possible. You may want to cover your work space with plastic sheeting for easier cleanup. Protect the bowl from the sun during the drying stage.
Step Two (Create Mold):
Prepare your mold by ‘sculpting’ a shape in the dirt (in garden patch or barrel) at least 4 inches wider and longer than the leaf you wish to use and about two inches deep on edges and a bit deeper in the middle, as shown. You can shape the mold as you wish. Try to ensure a fairly flat bottom and symmetrical shape. My first shape was more or less an oval. The second one was leaf-shaped.
Line the mold with a piece of your plastic sheeting, leaving lots of margin to work with, and spray heavily inside the mold-area with cooking spray. Secure the edges so they will not blow around while you are working. (I stapled the edges of the plastic to the whiskey barrel I used to mold in.)
Step Three (Cut Reinforcement):
Using wire cutters and wearing gardening or work gloves, cut a piece of the wire mesh roughly the shape of your mold but an inch or two smaller. Keep it ready to hand.
Step Four (Prepare Concrete):
Fill two pails with water—one for mixing and one for cleanup. Measure the concrete mix into a tub or wheelbarrow. For a bowl about 13 inches wide by 16 inches long I used 14-15 pounds of concrete mix. (I used a bathroom scale to roughly weigh the concrete powder. If you have to guess, try 14-15 trowelsful.) Mix the concrete by slowing adding water and stirring with a trowel until the mixture is the consistency of brownie batter (slides off the trowel in a moist clump). Too dry and it will crack, too wet and it will not shape easily.
If you wish to colour the concrete, now is the time to add a powdered colourant (or some say latex paint will also work but being a liquid it would have to be factored into the moisture content). Check with a hardware store for advice on a colourant. (Grout might work.) Mix in well or leave a “marbled” appearance as you wish.