Reflections in a puddle?
Mark the positions by getting someone to poke sticks into the reflection of each star?...
You'd keep to the same angles and just scale up the distances to whatever was convenient.
Except, there'd be an elongation effect due to the angle you were looking from (worse in winter when Orion's low) so the relative distances between the 3 stars would be pretty good (which it seemed to be) but the dogleg in the henges would be slightly overstated. Which it is, I think.