Hi all. This is my 1st time posting and if this has been answered somewhere else, please forgive me. I have been pouring over this forum for 3 days (bordering on obsession) and CANNOT neglect my kids, chores, etc anymore:) I could just kick myself at some of the things I've thrown away that could've been used for some amazingly creative uses! So, I've read several threads on using concrete for things. Particularly of interest to me is to make birdbaths and pond liners. I have never used concrete for anything other than filling a post hole so I am confused about how to make it rounded inside? Seems gravity would make it all pool at the bottom of the mold. Can someone explain? Please?