It seems to me that the Solar Cone Grill is easier to construct than the Solar Grill made out of sectors. In a solar cone grill, each cone can be cut out from a metal plate as each cone is a segment of a cirle with a given diameter. Each cone form a part of a parabolic shape heating excactly the same spot. The spot heated is depending on the size of the cones. Example of five cones solar grill: File:5 cone solar grill.jpg