The handiest thing I own for making flies out of foam is a battery powered rotary tool and a set of different diameter arbors. I can handle from 1/8" down to straight pin sizes. Dremel was very good to replace my variable chuck when it locked up with the arbors. I would do as Jim suggested with the flip flop foam and shape it where it could also portray salmon or trout eggs if colored correctly. We are all imitating things fish eat, this just happens to be something that comes out of a jar.