See above listed instructables for complete material lists, and tools needed to complete this project. I have shown the specific plastic bowl and bowling ball used.
Step 2: Provide For Drainage
As a gardener, I know that you must absolutely provide for drainage holes in any enclosed planter, else the plant roots will rot in the water that stagnates in the bottom of the planter. In order to provide that drainage in my planter, I decided to use a piece of PVC pipe cut to about 2 inches. This will be placed in the bottom of the mold and support the bowling ball, and allow for 2 inch sides, provide the necessary drainage and make it unnecessary to drill the concrete later on.
Step 3: Mix Concrete And Pour Into Mold
After coating both the bowling ball and the plastic bowl with a very light coat of vegetable oil, or a Pam like spray, the mold is ready to be filled. Mix concrete according to instructions and fill mold. I used 8 soup cans full of concrete to complete this pour.
Step 4: Decorate Concrete At This Point
I decided to decorate the lip of my bowl with glass beads available at any craft store. We had some on hand, so decided to use them up. You can wait up to 45 minutes or so to do this step, but I went ahead and completed it as soon as I had poured the concrete. A simple design was used, but tried to place them in a manner pleasing to the eye.
Step 5: Let Set Overnight Before Removing Bowling Ball
The concrete must set up to a point where removing the ball will not break the sides of the mold. After at least 24 hours, or longer, simply lift the ball out of the mold.