11 Unit squares packing puzzle

The inner square is the smallest known square that can fit 11 unit squares within in. Two of the squares are built in, with the other 9 being stored on the edges. The unit squares should press fit into the corner and slots, so there are some holes on the backside to help get them out.The solution produces a rigid packing, so after putting it together, the squares should stay in place unless you intentionally push one back out. The included 3mf adds ironing to the tops of the unit squares (including the two built-in ones, to help things look more consistent). As I was testing it, I found that using the theoretical value for the inner square size resulted in it being slightly too big (it permitted some other packings), so it is slightly smaller than the theoretical value. If this turns out not to work for you, you may want to resize the squares by a fraction of a percent, or you can edit my original design from https://cad.onshape.com/documents/1ab9d4c16d8162d97ac9302f/w/6c090bc9e523dc9b