Measure the length of the first stave (center or mother stave) and bend it on the hot bending iron to the exact shape of the form.
Rough carve it to shape with a carving knife or block plane. Then shape the stave on a planing table so that the edges lie flat when the bent stave is resting on a flat reference plate.
Glue the first stave in place by applying hot hide glue to the headblock, tailblock and mating underside of the tips of the stave. You can hold the stave in place with tape or push pins.