A method of assembling a prosthetic valve using sheets of material, such as pericardium material, polymer or bioengineered film, or other material. The method provides an accurate and repeatable system of making pericardial valves in which sheets or pieces of material are held securely in place relative to each other throughout the steps of assembling the valve. In addition, methods of the present invention include maintaining consistent alignment of the fixtures and pericardium material throughout the valve assembly process and utilize features that make the tooling components easy to assemble and handle. Certain aspects of the invention can be used to help establish a repeatable sewing and cutting technique for creating a pattern shape for valve leaflets, establishing stitch lengths, and determining the exact placement of stitches.