Sorry, but what you want is simply not possible -- you cannot turn something flat into something completely round. It's sort of like putting a square peg in a round hole. If you are upset with this situation, the next time you are in your place of worship you can take it up with the Great Geometer. Meanwhile ball manufacturers have learned to live with it. They use a stretchy material and clever seam patterns. Just go to a sports store and look at the patterns they have come up with. The smaller the patches, the less stretchy your material has to be to get a reasonable fit.

Chris