Poofy is probably the wrong word.  My hair is healthy, not dry, and no split ends.  It's even pretty shiny for blonde hair.  However, sleek is totally beyond my hair's capability.  It sort of rises like bread and from even a short distance away it looks frizzy.  And yet it is soft and silky to touch, like I said, no split ends.  Am I doing something wrong? 

I never roll my hair, no heat or harsh chemicals ever come near it.  But it seems like no matter how diligently I condition, jojoba oil, etc., I simply cannot get it to look sleek.  I do have a natural curl and that curl is what poofs out and looks frizzy rather than lying flat and looking sleek.  Living in Texas with a very humid climate certainly doesn't help, but surely there's something I can do?

I can run my wooden comb through it, or my hands over it, and it flattens down and looks sleeker for like all of 5 seconds before it starts lifting out again.  And that's inside my house and away from the humidity!

Any advice?  Would a coating of shea butter or maybe a henna gloss help make my hair lie flatter?  When would I apply something like this, while still wet after shampooing or later when dry but before combing?  I know I'm fighting against nature here, my hair is what it is, but does anyone know a natural, non-damaging way to get a sleeker look?

Thank you in advance for any and all help you can give me.

I'm going to have to agree with Sakira- there's not much you can do to make it completely smooth.
BUT, depending on how curly your hair is, there are some things you can do.

One thing I like to do is to braid my hair wet, at night, and put a roller on the end instead of a hairtie.  Then, the next morning, your hair is wavier and less curly, and there's a little ringlet on the end instead of the spastic way the ends dry if you  put a hairtie and let it curl.

Now, this works pretty well for me, but as you can see by my photo my hair is pretty curly.  If yours is only slightly curly then it might not make much of a difference, although it might smooth it a little.
Another option you can try is putting your hair in large rollers (FOAM only, not those awful spiky ones).  I don't like doing this, as my hair is long enough that it's hard to get the back sections in, and it's uncomfortable to sleep.

Maybe I'm just lazy, but the more I hear about rollers and all that, the more I like my hair just as it is.  Heavy sigh ...