I just looked up a template online for the hood. A google search of “altair (or ezio) hood template” will give you a lot of options. Hoods are never easy so just be patient and practice a little before making your actual hood. You may want to make a dummy hood out of spare or random material you have lying around to make sure all your measurements are correct and it looks satisfactory. I made my blade from a dresser drawer slide. I’ll put up pictures to explain the general procedure so stay tuned.
If you need any more specifics, just send me another ask. Good luck on your costume.