I had a rectangular birdbath made around New Year. Yet, I wanted to fulfill my dream of making a concrete birdbath on my own. To suit this plan, I had found a lampshade that had the right depth - about 2 inches in the centre.
I first took some sand and shaped the surface using the lampshade and smoothened it to the desired radius - about a foot wide. Then I spread plastic sheet on it carefully not to disturb the 'sand finish'. Now it was ready to pour concrete. After it had become hard by the next day, I removed it and turned it up. This picture shows with its bottom up. The circular design was made using the brim of plastic buckets of two sizes.
