Solar Ovens

caters: when I make a solar oven I know metal is the best material for the heat but how will I contain the heat? Which shape is best for what temperature?
Here is a list of temperatures both oven and stove

Oven:
200
225
250
275
300
325
350
375
400
425
450
475
500
broiling

Stove:
Low heat
Medium Low heat
Medium heat
Medium High heat
High Heat