A technique has been developed recently to fabricate SiGe film islands on a glass layer, which in turn lies on a silicon substrate. The islands are initially under an inplane compressive strain. Upon annealing, the glass flows and the islands relax. The resulting strain-free islands can be used as substrate to grow epitaxial optoelectronic devices. This paper models the annealing process. A small island relaxes by inplane expansion. Because of the viscosity of the glass, the relaxation starts at the island edges, and moves toward the island center. A large island wrinkles before the inplane relaxation reaches the center. After some time, the wrinkles may disappear when the inplane relaxation arrives. Alternatively, the wrinkles may cause tensile stress in the island, leading to fracture. We model the film island by the von Karman plate theory, and the glass layer by the Reynolds lubrication theory. The solid and the fluid couple at the interface by traction and displacement continuity. The inplane displacement and the vertical deflection evolve simultaneously. A combination of experiments and calculations describes the conditions under which the islands relax by inplane expansion without significant wrinkling and fracture.