I just got some EasyCast. The shape I want to make isn't flat-backed -- for simplicity's sake, let's call it a sphere. I'm wondering if I can avoid using a two-part mold, with the resulting headaches of pour sprues and air vents. I'm thinking of making two one-part molds, and gluing the resulting casts together. Would the backs be flat enough? And are there other problems with this idea that I'm not seeing?
Input would be appreciated. I can always figure it out through trial and error, but I'd rather not waste the time + materials.