This shows the proper placement position for putting your cleaned lens back in the camera. One side has flat edges and this goes forward. You might be able to recognize this side from the wavy washer imprints it might still possess. The side with a bevelled edge is the side that points back toward the film.

Some people have reported interesting results by reversing the lens. If you want your Brownie Hawkeye to perform in the normal manner, put it back like it came apart. But, if you have a spare Brownie Hawkeye, you might want to experiment with it and reverse the lens direction for some cool effects. Pictures that I've seen taken with the lens reversed produce an image where there is a "sweet spot" of good focus in the middle of the photograph with lots of blurriness around the edges. For certain subjects, it's a very interesting effect!