For the Long-EZ:
After laying out the dimensions and sanding the depressions in the side of the fuselage, you glass the inside of the fuselage sides only (chapter 5, steps 1 & 2).
With the foam sides glassed on the inside only, you can easily bend them enough to mate up with the bulkheads. Once the sides and bulkheads are bonded together (chapter 6 step 1), you carve the outside of the fuselage to shape and then glass it (chapter 6 steps 2 and 3).
The Cozy, E-Racer and other side by side designs use a jig to build in the curvature of the fuselage as it is a more severe curve and some "pre bending" of the foam is desired before glassing the inside. This technique could be used for the Long-EZ but is not required.