Cut out carefully into 4 sections: 2 arcs and the concave and convex piece. Be sure the curves are smooth! On the left over FP, trace the triangles of the arcs. Use these to cut the corresponding fabric 1/2" bigger all the way around.
On the cut out arc, sew on the lines of the triangles with no thread in the machine. These perforations will help to fold the arcs accurately.