Go for 360 degrees with the front lower than the back. If you can make the sections so the top is wider than the bottom so the reflector spreads out like a flower, that can help. Use an oven bag, not just a ziplock.

Set it up and ignore it for hours, unless you see something strange developing. Once you open a small solar set up's thermal isolator / bag it takes a long time to get back up to temperature.

Have fun and give us a report!

Edit: I put a 4.47 pound roasting chicken and some veggies out to cook in my cardboard box solar cooker at 10 am today. It is 11:45 and the pot is too hot to touch for more than a second and I can see the chicken browning where the lid is lifted about ½ inch because I overloaded the pot.