I do whatever with them, but try my best to keep them handy and unfolded. Not always easy. It depends on the clothing, and the bag. Usually, I travel in casual clothing, so shirt pockets are not available. Back pocket sometimes, but that's risky because they fall out easily.

Honestly, the shape is outdated. I think Virgin America has passport-sized BPs, and that would be great for other airlines as well. Of course, a passport is not always necessary, but that size would fit in a pocket easily without the need for folding.