Joint owenership in flat with wife

You can make a settlement deed in favor of your wife. The settlement deed  should be compalsorily registered and stamped as per the rates prevalent in your state because as per section 17 of the Registration Act an interest in the immoveable property would be created in favor of your wife which was hitherto not there.

As per the Indian Stamp Act, 

 “Settlement” means any non-testamentary disposition, in writing, for movable or immovable property made-

         (a) In consideration of marriage, 
         (b) For the purpose of distributing property 
         of the settlor among his family or those for whom he desires to provide, or for 
         the purpose providing for some person dependent on him, or
         (c) For any religious or charitable purpose; and includes all agreement in         
         writing to make such a disposition and, where any such disposition has not 
         been made in writing, any instrument recording, whether by way of 
         declaration or declaration of trust or otherwise, the terms of any such 
         disposition;
The said definition is wide enough to cover the kind of disposition you intend to make through which you would give up your claim of absolute ownership of the property and constitute your wife as a joint owner along with yourself.