The Perfect DIY Solar Oven : 6 Steps (with Pictures) - Instructables
Take the overall width of your oven (W) and multiply the factor in the drawing to get the dimensions for your windshield. Start with measuring your suncover and fold it along the cutout for the mirror. Refer to the picture (s) above. This should serve as the fold at the base. Measure up the distance to the right distance and cut the opening.