I haven't done this, but you know those large foam kids puzzles? You can use those (or other things of the same type material), cut the shape you want , heat slightly with heat gun and then press onto any raised/textured surface. Ta-da a new stamp!
(middle school in Oregon)
>>>>>>>>>>I read in a magazine about someone that used foam from a
garden kneeling pad and a wood burning tool to create stamps - has
anyone done this?