How to split and iron straws
How to split flat straws to the width you want

Once you have a flat straw you can take a corsage pin, poke it thru your straw then pull the straw while holding down the pin. If you start from the middle, after you cut one side flip the flat straw and put the pin into the cut and pull away from the cut side.
I find that this is often the easiest way to get the width of straw you want especially when you need very narrow splints.
You can even half the width of a splint you have run thru a splitter. As it is almost flat no need to iron it first.