I don't see a flaw in the technique you are using. The "dizzy feeling" (which is probably the vibrational state) means you are getting there.
This is a technique I like to use:
Meditate until very relaxed, then lie down on your back, relax a while if you snapped out of the meditational state while changing positions, let yourself doze off a bit so you are almost dreaming (you see random pictures and scenarios as you would a dream but are awake). Hold that state and try to project. Try lifing just one arm, leg, etc just to see how it feels at first. (Fuzzy, dizzy, warm feeling are good signs).
Also, make sure you don't hold any unrealistic fears of the astral plane-nothing bad will happen. Your physical body cannot be possesed while you are visiting the astral plane.
When I started working with astral projection I had the vibrational state down after a few months but it took several months after that to succesfully project. Keep at it, the experience is worth the time and effort!