It would be difficult to complete your Bradley Base project with out a form. The single, or half, version of this form (LB-5) is used for wall sconces, and the double, or whole, version (LB-10) is used for torches and lamp bases.
Before using the LB-10 as a lamp base form, you must cement the two halves together with your own personal clear silicone glue. The widest dimension at the shoulder is about 9-1/2", and it is about 15" high.