What’s the easiest/cheapest way to make a map board for the bike ?

Mine’s just a plastic chopping board cable tied to the bars and stem.

TQ map (2) by Vegan Graham, on Flickr

That’s the Mark 1 version.
The Mark 1a has got two more holes at the front and a boot lace down to the fork crown to stop the wind lifting it at high speed.
I’m currently on the Mark 1b which has got P clips and bolts with big washers to hold it to the bars because the cable tie holes were starting to split.

I used an A4 clip board cut down to size, Made some holes and zip tied to secure.

I got a rubberised cutting mat (A4 sized) from an art shop, drilled 4 holes through it and cable tie it to the bars. The fact that it bends a little is quite welcome if you take a trip over the bars

Those temporary corrugated style plastic road signs work quite well I hear.

Would that be the road signs that are made out of the same corrugated plastic as estate agent’s signs ? 😉