Many years ago, before they let us be TAs in grad school they made us do a teaching presentation. I did mine in explaining number systems and the binary system. Your point about donuts reminded me that I tried to explain number place as putting things in boxes. The units are single items. When you get to tens, it's too many to handle loose so you put them in boxes and count the number of boxes and so on. If I am ever called to teach it I'll need to to find some item that I can put in boxes at least into the thousands. The problem is I can't think of anything that is naturally sold in boxes of ten. I guess that is again why the duodecimal is better. Under the duodecimal I would create stacks of 2x2x3 or 1x3x4 if I want to be in a plane. Under the decimal I would have to do 1x2x5.