"Many Dutch people put hagelslag on their bread."
Translation:Veel Nederlanders doen hagelslag op hun brood.
To me it sounds like you put the package on top of the sandwich instead of sprinkling the chocolate on. (like Yruzz explained for "zetten"). Putting sprinkles on your sandwich is not such a deliberate(?) action to use *placing the sprinkles, it sounds like making art. You could use "strooien" instead of "doen". It would translate in "sprinkle sprinkles on their bread".