clousers

Tying the barbell eyes on the other side of the point is what makes the fly ride that way in the water.

D-mac is right, the weight of the eyes cause the fly to flip hook side up.
 
Caveats: the eye has to be heavy enough, compared to the hook, to cause it to flip. A light eye on a heavy hook might not do the trick. Also the barbell eye has to be positioned 1/3 of the hook shank length behind the eye. An eye that is too far forward -- close to the hook eye -- will cause your clouser to act like a jig.
 
The Clouser should ride upside down, relatively level and have a bob in its action. But it shouldn't flip over and head nose first for the bottom like a jig. 

Use a loop to attach it to your tippet.
 

ORIGINAL: ><>er man

put your hook in the vice the way you want want it to ride and tie the dumbbell eyes under the hook shank 

 
 
I find it easier to put the hook in the vise the normal way and tie the barbell eyes on top of the hook. Then turn the hook over to finish the fly. That's how I do my crayfish flies.

Additionally, you can use jig hooks and tie clouser eyes on them.  I do that a lot when I want a bigger gape hook in a lighter wire.  Mustab bronze hooks work well.  You also don't have to tie the eyes on the back side with them.  I tie them on the inside of the bend, right below the eye.  They work really well that way and there is nothing on the bottom of the hook to get caught in weeds and light brush.  They slide through cover better it seems.
 
Contrary to above, I do tie mine a little heavier in the eyes so that they are more like a jig.  If I wanted it to sink horizontally, I'd fish a normal streamer.  The point of a clouser is (1) to ride hook point up for less snags and better hooksets/position and (2) the nose first action when it is going up or down.  A natural baitfish that is struggling will fall nose down or swim nose up most times than not in my experience.

Thanks,
Rick