I’d use binder clips in place of the Velcro, but that’s just me. I have once of these sun shades in my car’s trunk (yeah, it keeps the trunk cool…). I think I’ll pull it out and have a go at this on my next camping trip.
Take a $3 reflective car windshield sunshade, sew some Velcro tabs along one edge, then fold the shade into a funnel shape. Viola!
Here’s the list of needed materials…
A reflective accordion-folding car sunshade – a cake rack (or wire frame or grill) – 12cm (4 ½ in) of Velcro – black pot – bucket or plastic wastebasket – a plastic baking bag.