a) I like making a ground blind on the go with some camo net around 2-3 trees. Not really tall, just enough to break my outline, about a yard high from the ground
As long as my jaket blaze orange can be seen through the holes in the net and some part of me can be visible above the net (say head, when I am not hiding behind the net mode) - I am satisfying blaze orange requirements (and I have a few cheap blaze orange jackets to put above the net on a branch to make it sure).
(my source - word of a game warden, I hope such understanding is universal among them

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b) I don't know about Illinois, but in Wisconsin, if you get a full-size ground blind, you need to have 144 sq inches of blaze orange visible from any direction... And I haven't seen any blind on sale satisfying that requirement.