A flange is designed to sit with its lip on top of the finished floor with no gap under it. The type you have, I don't know . All current flanges that I've seen have screw holes around it to anchor it to the subflooring and the slotted holes to insert the bolts to hold the toilet down. The whole portion above the floor is normally not much more than 3/16-1/4" above the finished floor. For many toilets, if it exceeds that, you can't get it to sit flush. My unprofessional opinion.