I take a can of spray paint for inverted use in ground marking, and I just spray an X at the center. Harms nothing, cannot trip on it and after years now, no one has ever complained, even on a school yard.

Gary

i do a fun fly i mark a x for center with  5ft circle around it for center

Your not gonna trip over a little rag. You don't pivot on the rag, just put it down as a reference point like 10' away.