Restraining glass flow requires the use of kiln furniture such as side walls and dams.  In Tipsheet 3: Working Deep and TipSheet 5: Bullseye Box Casting, we discuss the fundamentals of using these tools in the context of specific kilnforming methods.  We also recommend watching our video lesson: “Kiln Shelves and Furniture“.
Many of our video lessons also demonstrate how to restrain glass flow in contexts related to the project or method being discussed.