It was Rusty Gates who showed me how to tape sinle edged blades together with spacers to make zonker strips from rabbit hide. Looks to me that same thing would work on that foam.
Now for the the questions...

How about a how-to on making the indicators themselves? I don't have any to use as a model but I do have lots of foam sheets!
Is it true that some of the craft foam sheets like those at Michaels and such aren't truly closed-cell foam and thus take on water?