Search "foam shaping" Eric Gordon's post may be what you were thinking of

Someone showed how to cut and glue the foam into a bolster. But I can't remember how to cut it.

Peter,
I don’t know how if you can repost a thread but if you enter foam shaping in the forum search bar it brings up the post where Eric shows cutting a square from edge of foam and gluing the edges together
I believe that’s what your looking fore