I found a mixing bowl!
 

Now I feel kinda stupid. All this talk of flat bottomed bowls made me go
look in the cupboard to see what the stainless steel bowls look like that I
bought for peeling garlic. They are flat inside but the flat portion is far
smaller than the new ones that I bought.

But... What did I see at the back of the cupboard? My fancy cut glass
salad bowl (wedding gift) was back there but I could see glass over it. It
was a mixing bowl! The one that I bought to replace the big blue one that
got broken. I had forgotten all about it because I can't really nest my
other mixing bowls in it. Those bowls are a slightly different shape and if
I put them inside, they go in so deeply that they are hard to get out. I
believe this one is a Pyrex and it's a clear blue glass. I never really
liked the looks of it although it is perfectly functional. There is just
something about the color of it that makes me think that it isn't really
clean. It is clean. It just has some sort of unattractive hue to it. It
isn't a pretty blue. At any rate, if the stainless bowls won't work for
whatever reason, I can always use that one.