I would like to solar cook in the winter here in S.E Pa.
I've read some articles about tilting the box cooker(one reflector), I don't remember forward or backward with rocks underneath the back or front. Which is it?
Thank you ...? for your question.
You surely can solar cook in the wintertime in Pennsylvania, all you need is a sunny day.
We have many site visitors, colleagues and others who do so successfully, even people up in Canada and northern Europe. Of course they may not have as many sunny days as some places do in the winter, but when they do they surely like to take advantage even if the time frame on such a day is short.
As for your cooker and the angle; if you can move the panel forward and backward (up and down) you can reflect the sun into the box cooker by using a lower (down) angle when the sun is low and a higher angle as the sun rises.
If your reflector panel is set and immovable then you would need to tilt the whole cooker in the same manner; if the sun is low tilt the cooker and panel forward using a rock or such in the back and do the opposite when the sun is higher in the sky. You should be able to also see the reflected sun (light) as you move the panel/cooker about and can work the reflected light concentration until it reflects into the box interior.
I hope this is helpful and that I have explained myself well enough. If not, maybe someone else can put it into "plainer english" than I.
Good luck with your solar cooking.