Any of you have any experience making squirrel nest boxes? What are some features i need to incorporate into building a good nest box?

I think a while ago, there was a thread about squirrel nesting boxes. There was a video of a guy making them out of old tires.

2zwudz -

I've never made specifically squirrel boxes. However, I constructed and put up several hundred owl nest boxes over many years, which got use from red squirrels, flying squirrels, kestrels, ducks, flickers, and marten. You need to be diligent about cleaning them out each fall and putting in new wood chips in the bottom of the box to prevent freezing of the newborns. For squirrels, do not use OSB or plywood, use cedar or redwood planking. The glues in the plywood apparently taste good to a squirrel, and they chew them relentlessly. Good luck!

Spouse put up some in our tress, old ferret nest boxes. ^^^^ those would work great.

I would not encourage them, soon you will have squirrels out your ears and they will chew on everything.
We have had a few you could pet once they get used to you feeding them.