Are you making the hood or do you already have a hood? If you're making it, go with a pattern like this: [link]
and sandwich the ears into the seam before you sew. (If you are making a hood and that didn't make sense, lemme know and I'll clarify.
) But if you're sewing them onto a hood after the fact, try the hood on and make chalk markings where you want the ears to go. I think you could then probably get away with just sewing the ears directly to the outside of the hood without cutting a slit into it. Just make sure to finish your edges. Hm, give me a day or two and I'll update the tutorial with new methods.