Buy a cooker
First, you could build your own and start experimenting, or if you are more of the adventurous type and ready to jump, you may want to get a commercial cooker.
If you like to use the solar cooker for camping trips, weight and size may be important. A panel cooker is very light weight and folds up and so it uses little space, both when traveling and when in storage. Panel cookers get to temperatures of about 100C without problem on a nice sunny day (blue sky). Things cook slowly in the panel cooker, so it is not something you would want to take out ½ an hour before you want to eat. It is also hard to boil water for tea or coffee, in fact, probably very impractical for it. But please note that you do not need to reach 100C to cook rice, potatoes or vegetables or some meat or fish. They do get cooked at above 80C just fine. It is good to have some thermometer available.
Another possibility is to use a ‘fast’ cooker. Such as the SunPlicity which is a parabolic cooker and has the really nice advantage of being able to fold up. Not many can do that. Both when not in use and when in transport the cooker takes very little place. You can fry things, cook food almost as you would on a gas range or on an electric stove. It is not quite as strong – depending to radiation level it provides approximately 400Watts, enough to bring 1 liter of water to boiling in ½ hour.
If you plan to use the cooker at home, you need to make sure you have a sufficient access to the sun. For example, a north-facing apartment in a high-rise building is poorly suited to regular solar cooking, for obvious reasons. A commercial box cooker can weigh 9 to 12 kg and is clearly not practical if you need to take it outside to a park in order to cook. If you have a balcony facing in the direction between south-east and south-west you should be getting sufficient direct radiation for many days in the year. If you live in a private home and you have a spot outside that receives radiation during several hours per day, that is of course ideal, needless to say that shades from trees may ruin the fun. That sunny spot may move during the year as the position of the sun in the sky changes during the seasons, not only from hour to hour. You can leave the cooker in a given place and cover it like you would cover a grill to protect the cooker against dust and rain. Either a box cooker such as the SunTaste or a parabolic type fast cooker can work well. Note that a parabolic type cooker has to be moved, which we call “sun-tracking”, to capture the direct radiation of the sun every 20 minutes or so, while the box cooker can stay put for up to 2 hours and sometimes even longer.