After finding a northern flying squirrel in a bird box in the fall of 2012 I began testing out flying squirrel nest boxes. After trying out the only design I could find and its resulting very limited use I began to alter it and use a completely different design that flying squirrels were using. 

The two different designs are two completely different designs. One is a more traditional nest box with a entrance hole on the side near the tree truck for easier access. The second design has an entrance on the back side of the box against the tree with a roof that covers the entrance and provides a gap between the entrance and the tree trunk.

One "problem" I have had so far is the flying squirrels at one location are fatter than normal due to access to bird feeders. Because of this they require a larger hole size than "normal" wild flying squirrels.