Here's what you need:
The traditional German cheese for this is "Gouda". If you can't get it in
your region, you may try some similar sort. Go for the "big boring one".
Make sure you buy an cheese that is not famous for having any special
taste and comes in big chunks. Depending on where you live, this may
be cheddar, havarti, brick, etc. See World Cheese Index
The choice of a good boring cheese is of elementary importance.
Just any will do.
3. Flag picks
In Germany you can buy these in every larger store. If you live outside
Germany, you may have to work with toothpicks and a printer. Maybe
later I will add an extra instructible on this issue. Needless to say that
by all means it has to be a German flag.