1/2 the flour
1/2 the cornmeal
The other 1/2 of the flour
The other 1/2 of the cornmeal
As long as your ingredients are relatively the same texture, you can really put them in whatever order you like because they're just going to get mixed together eventually anyway. The thing to keep in mind with layering is that you want to put the heavier ingredients toward the bottom and any ingredients that will have space between pieces (like chocolate chips or beans, for example) are on the top. That way flour or whatever doesn't filter down in between them and make your layer look funny. Making the layers vary from light to dark colors makes it look really nice too. Just look how good these muffins in a jar look!
You want to try it now, don't you? Well, my culinary friend, here is a website that has tons of ideas for mixes in a jar to get you going. Happy mixing!