Solar Ovens work by collecting and focusing sun light. Here is a simple diagram. of one style.
Some dispense with the transparent cover and simple collect and focus the light.
You can even make one out of a cardboard box and foil.
That last one is one I made some excellent enchiladas in during a camping trip.
Here is one that works great on a boat and is easy to transport.
They all share the same principal. Collect and focus the sunlight.
8 Best Solar Ovens
Based on dozens of customer reviews and ratings, the followings are the top 8 best-selling Solar Ovens: