Phoenix eyes can be slanted to a small, or large degree. So you can use the makeup guidelines here according to what you'd like to do.
It's really up to you and your mirror. Do you want to emphasize the slant, on downplay it? Do you want to make them longer, more rounded, or flatten them out into an intimidating squint?
I'm going to be using the term 'phoenix' interchangeably with 'slanted' eyes. This is because the makeup here is generally suitable for any eye that has an upward angle.
A lot of makeup techniques are usually aimed at giving someone the look of phoenix eyes, because they're just so bad-ass and sexy. They seem to just be telling you to back off and wait for me to come to you... because it's you that I want... but in my own time... :)
I think most women with these eyes may have this problem- tons of men thinking that they want them- just because they looked at them. I know that's what I'd think if I was one of those assuming simpletons.
Okay, away from the man bashing. Men are great. Until they come across a phoenix eyed woman... Which is why the cat eye is so popular for those of us with regular straighter lash lines:)
If you are blessed with natural cat eyes though, first start by determining the eyebrow shape that will do you the most justice, and then explore different ways of applying color.
A curved brow softens your look, while a straighter eye gives you a more intense look. A high arch though, adds more angles to to your profile. It's harsh for your face, so it's not very flattering...
The best route to definition is to follow the lines of your eye shape. Use eyeshadow patterns that outline the linear form of your eye. Horizontal patterns will especially work if you have mono lids.
If you choose vertical ones, then the darker color is placed on the outer part of your lids. It looks better when you also combine that with placing that dark color along the bottom part of your lid, and wing the eyeshadow a little.
The effect sharpens the shape.
The best eyeliner shape will be along your top lid with uniform thickness. If you line the bottom lash line, do it the whole way across. Blend the liner to soften it, because your eye already has a sharp angle. Blended liner defines but also is not harsh...
Sometime it's nice to look a little different to the way you usually do. If you want to do so here's how.
Your main focus should be the use of eyeliner. So without making any obvious patterns with your color, apply a one or two color shadow.
If you'd like to play around with color, apply the darker shadow on the outside half of the lid, without winging it.
You already have the shape that most people try to create with the classic three color palette, so use simpler patterns with light and medium colors.
For your eyeliner, start by tight lining the upper lash line. Then apply liner all the way across, making it thicker on the outer corner of the eye.
Then line halfway across the bottom lash, making that line thicker on the out side too. This is the key to lowering that angle... The thickness at the ends makes that part of the eye look heavier. If someone is looking at you, their eye is also drawn to the ends of the bottom lash. Illusions, illusions...
Blend it out so that it's soft. This way it doesn't make you look too hard and angular.
Apply mascara, with a few more swishes on the outer lashes.
Phoenix eyes can also be round, so this will most likely make them even more rounded, if they're round to begin with...Makeup Know How > Eye Shapes > Phoenix Eyes